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Cross Site Scripting

Cross Site Scripting, also known as XSS, is a type of web vulnerability that allows attackers to inject malicious code into web pages viewed by other users. This can allow attackers to steal sensitive information, such as passwords and session cookies, or perform actions on behalf of the user, such as sending unauthorized emails or making unauthorized purchases.

Types of Cross Site Scripting

There are three types of Cross Site Scripting:

• Reflected XSS: In this type of XSS, the attacker injects malicious code into a web page that is then reflected back to the user. This can happen when a web application does not properly validate user input.
• Stored XSS: In this type of XSS, the attacker injects malicious code into a web page that is then stored on the server and served to other users who view the page.
• DOM-based XSS: In this type of XSS, the attacker injects malicious code into a web page that is then executed by the victim's browser.

Preventing Cross Site Scripting

There are several steps that web developers can take to prevent Cross Site Scripting:

• Input Validation: Web developers should validate all user input and sanitize any input that could be used to inject malicious code.
• Output Encoding: Web developers should encode all output to prevent malicious code from being executed.
• HTTPOnly Cookies: Web developers should use HTTPOnly cookies to prevent attackers from stealing session cookies.
• Content Security Policy: Web developers should use Content Security Policy to restrict which sources are allowed to execute scripts on their web pages.

Conclusion

Cross Site Scripting is a serious web vulnerability that can have devastating consequences for users and web applications. By following best practices for web development, developers can help prevent Cross Site Scripting and protect their users' sensitive information.

For more information about Cross Site Scripting, visit the OWASP website.

Cross Site Scripting Payload List

Cross Site Scripting (XSS) is a type of security vulnerability that allows an attacker to inject malicious code into a web page viewed by other users. This can lead to theft of user data, session hijacking, or other forms of cyber attacks.

XSS attacks can be classified into two types: reflected and stored. Reflected XSS attacks occur when the user input is immediately reflected back to the user, without any input validation or output encoding. For example, if a search form takes in a user's search query and displays the results without any validation or encoding, an attacker can inject malicious code into the search query and have it executed by other users who view the search results.

Stored XSS attacks occur when the user input is stored on the server, and then displayed to other users at a later time. For example, if a user can post comments on a forum, an attacker can inject malicious code into the comment and have it executed by other users who view the comment.

Here is a list of common XSS payloads:

• Basic XSS Payloads

• <script>alert("XSS");</script>
• <img src=x onerror=alert("XSS");>
• <svg/onload=alert("XSS");>

• Advanced XSS Payloads

• <video poster=javascript:alert("XSS")></video>
• <iframe srcdoc="<script>alert('XSS')</script>"></iframe>
• <marquee onstart=alert("XSS")>XSS</marquee>

It's important to note that XSS attacks can be prevented by implementing proper input validation and output encoding on the web application. Input validation ensures that the user input conforms to the expected format, while output encoding ensures that any user input displayed on the web page is properly sanitized to prevent any malicious code from being executed.

OWASP (Open Web Application Security Project) provides a number of resources to help developers prevent XSS attacks, including the OWASP XSS Prevention Cheat Sheet and the OWASP Cross-Site Scripting Prevention Cheat Sheet.

Web application security is an ongoing process, and it's important to stay up-to-date on the latest security vulnerabilities and best practices for preventing them.

Cross Site Scripting Exploit

Cross Site Scripting (XSS) is a type of security vulnerability that allows an attacker to inject malicious code into a website, which can then be executed by unsuspecting users who visit the site. This can lead to various consequences, such as stealing sensitive information, compromising user accounts, or spreading malware.

Types of XSS Attacks

There are several types of XSS attacks, including:

• Reflected XSS
• Stored XSS
• DOM-based XSS

Preventing XSS Attacks

There are several measures that can be taken to prevent XSS attacks, such as:

• Sanitizing user input
• Using input validation techniques
• Using content security policy (CSP)
• Using HTTP-only cookies
• Using secure coding practices

Learn More About XSS Exploits

If you want to learn more about XSS exploits, check out the following link:

https://owasp.org/www-community/attacks/xss/

XSS Bounty: What You Need to Know

XSS (Cross-Site Scripting) is a type of security vulnerability that allows attackers to inject malicious code into web pages viewed by other users. To combat this threat, many organizations offer XSS bounty programs that reward security researchers for identifying and reporting XSS vulnerabilities.

How XSS Bounty Programs Work

XSS bounty programs typically provide a set of guidelines and rules that security researchers must follow when testing web applications for vulnerabilities. Once a vulnerability is identified, the researcher can submit a report to the organization running the program. If the vulnerability is confirmed and deemed significant, the researcher may be eligible for a reward.

Examples of XSS Bounty Programs

Many major companies and organizations offer XSS bounty programs, including Google, Facebook, Microsoft, and Mozilla. These programs typically offer rewards ranging from a few hundred to several thousand dollars for each vulnerability identified.

If you're interested in participating in an XSS bounty program, it's important to familiarize yourself with the program guidelines and rules before you start testing. Additionally, make sure to report any vulnerabilities you find responsibly, and avoid any activities that could be construed as malicious or harmful.

For more information on XSS bounty programs and how to participate, check out the OWASP XSS Filter Evasion Cheat Sheet.

Why XSS Bounty Programs are Important

XSS vulnerabilities can have serious consequences, ranging from stealing user data to redirecting users to malicious sites. By offering bounties for identifying and reporting these vulnerabilities, organizations can incentivize security researchers to help identify and fix these issues before they can be exploited by attackers.

Furthermore, XSS bounty programs help to promote a culture of responsible vulnerability disclosure and collaboration between security researchers and organizations. By working together to identify and fix vulnerabilities, we can create a more secure online environment for everyone.

How to Participate in an XSS Bounty Program

If you're interested in participating in an XSS bounty program, there are a few things you should keep in mind:

• Research the program guidelines and rules before you start testing.
• Make sure you have permission to test the web application for vulnerabilities.
• Test the application thoroughly, using a variety of techniques to identify potential vulnerabilities.
• Report any vulnerabilities you find responsibly, following the program's reporting guidelines.
• Avoid any activities that could be construed as malicious or harmful.
• Be patient - it may take some time for the organization to confirm and reward your submission.

1. Google Vulnerability Reward Program

Google offers rewards ranging from $100 to $31,337 for finding XSS vulnerabilities in their web applications.

https://www.google.com/about/appsecurity/reward-program/

2. Facebook Bug Bounty Program

Facebook offers rewards starting at $500 for finding XSS vulnerabilities in their web applications.

https://www.facebook.com/whitehat

3. PayPal Bug Bounty Program

PayPal offers rewards ranging from $100 to $10,000 for finding XSS vulnerabilities in their web applications.

https://www.paypal.com/us/webapps/mpp/security/reporting-security-issues

4. Microsoft Bug Bounty Program

Microsoft offers rewards ranging from $500 to $20,000 for finding XSS vulnerabilities in their web applications.

https://www.microsoft.com/en-us/msrc/bounty-xss

5. GitHub Bug Bounty Program

GitHub offers rewards starting at $555 for finding XSS vulnerabilities in their web applications.

https://bounty.github.com/

6. Shopify Bug Bounty Program

Shopify offers rewards starting at $500 for finding XSS vulnerabilities in their web applications.

https://hackerone.com/shopify

7. Dropbox Bug Bounty Program

Dropbox offers rewards starting at $216 for finding XSS vulnerabilities in their web applications.

https://www.dropbox.com/security

8. Uber Bug Bounty Program

Uber offers rewards starting at $500 for finding XSS vulnerabilities in their web applications.

https://www.uber.com/us/en/security/report/

9. Airbnb Bug Bounty Program

Airbnb offers rewards starting at $100 for finding XSS vulnerabilities in their web applications.

https://www.airbnb.com/terms/host_guarantee

10. Mozilla Bug Bounty Program

Mozilla offers rewards ranging from $500 to $5000 for finding XSS vulnerabilities in their web applications.

https://www.mozilla.org/en-US/security/client-bug-bounty/

Top 10 XSS Recommended Tools

1. OWASP Xenotix XSS Exploit Framework

https://github.com/OWASP/Xenotix-XSS-Exploit-Framework

2. XSStrike

https://github.com/s0md3v/XSStrike

3. XSS Chef

https://github.com/faizal200x/XSS-Chef

4. DOMinatorPro

https://github.com/OffensivePython/DOMinatorPro/

5. XSSYA

https://github.com/yasserjanah/XSSYA

6. BruteXSS

https://github.com/shawarkhanethicalhacker/BruteXSS

7. Reflected XSS Scanner

https://github.com/stamparm/DSSS

8. XSS-Freak

https://github.com/PR0PH3CY33/XSS-Freak

9. XSS-Detector

https://github.com/stamparm/xss-detector

10. XSS-Payloads

https://github.com/payloadbox/xss-payload-list

Note: Use these tools only on authorized and ethical hacking engagements to avoid breaking the law.

How to Test Against XSS?

Cross-Site Scripting (XSS) is a common security vulnerability that allows attackers to inject malicious code into a website or web application. This can lead to various forms of attacks, such as stealing user credentials or personal information, hijacking user sessions, or even damaging the entire system.

Therefore, it is crucial for web developers and security testers to be able to identify and mitigate XSS vulnerabilities before they can be exploited. In this blog post, we will discuss some of the best practices and tools for testing against XSS.

1. Input validation and sanitization

The first line of defense against XSS attacks is to validate and sanitize all user input that is received by the application. This includes not only form fields and query parameters but also any data that is stored in cookies, headers, or other HTTP request components.

Input validation refers to checking that the user input conforms to the expected format and range of values, while sanitization involves removing any potentially dangerous characters or sequences that could be used for XSS attacks. For example, input validation can check that an email address contains the @ symbol and a valid domain name, while sanitization can replace any angle brackets (< and >) with their HTML entity equivalents (< and >).

2. Output encoding

Even if input validation and sanitization are performed correctly, there may still be cases where user input is reflected back to the user in the form of output, such as HTML pages, JSON responses, or error messages. In these cases, it is essential to apply output encoding to prevent any malicious code from being executed.

Output encoding refers to converting any special characters or sequences into their corresponding HTML entities, so they are displayed as plain text rather than interpreted as HTML tags or scripts. For example, the less-than symbol (<) can be encoded as <, and the script tag can be encoded as <script>.

3. Content Security Policy (CSP)

A Content Security Policy (CSP) is a security mechanism that allows website owners to specify which sources of content are allowed to be loaded and executed on their pages. By defining a whitelist of trusted domains and content types, a CSP can prevent unauthorized scripts or other resources from being loaded, even if they are injected by XSS attacks.

For example, a CSP can allow only scripts that are loaded from the same origin as the page (self), or from specific trusted domains (e.g., script-src 'self' www.google-analytics.com). Additionally, a CSP can restrict the use of inline scripts or eval() functions, which are often used by attackers to bypass input validation and sanitization.

4. Automated vulnerability scanners

Finally, there are many automated vulnerability scanners and testing tools that can help identify and report XSS vulnerabilities in web applications. These tools use a combination of static and dynamic analysis techniques to detect patterns and behaviors that are indicative of XSS attacks, such as the presence of script tags or the use of unvalidated user input.

Some popular XSS testing tools include OWASP ZAP, Burp Suite, and Acunetix, among others. These tools can be used to perform both manual and automated testing, depending on the level of expertise and resources available.

XSS Recommended Reading

If you're interested in learning more about cross-site scripting (XSS), here are some recommended resources to check out:

1. OWASP XSS Prevention Cheat Sheet

The OWASP (Open Web Application Security Project) XSS Prevention Cheat Sheet provides a comprehensive guide on how to prevent XSS attacks. It covers various types of XSS attacks, how they work, and how to mitigate them. The cheat sheet is regularly updated to include the latest trends in XSS attacks and prevention techniques. Check it out here.

2. XSS Attacks: Exploits and Defense

This book, written by Seth Fogie, Jeremiah Grossman, and Robert Hansen, provides an in-depth analysis of XSS attacks and how to defend against them. It covers various techniques used by attackers to exploit vulnerabilities and provides practical guidance on how to prevent them. You can find the book on Amazon here.

3. PortSwigger's Web Security Academy

PortSwigger's Web Security Academy provides a wide range of free online courses on web security, including a dedicated section on XSS attacks. The courses cover various aspects of XSS, from basic concepts to advanced techniques used by attackers. The Web Security Academy also provides hands-on labs where you can practice identifying and exploiting XSS vulnerabilities. You can access the Web Security Academy here.

4. Google's XSS Game

Google's XSS Game is a fun and interactive way to learn about XSS attacks. The game consists of a series of challenges where you have to find and exploit XSS vulnerabilities on a simulated website. Each challenge is designed to teach you a specific aspect of XSS attacks, from basic to advanced techniques. You can play the game here.

5. Cross-Site Scripting (XSS) Prevention

This article by Microsoft provides an overview of XSS attacks and how to prevent them in ASP.NET applications. It covers various prevention techniques, including input validation, output encoding, and using security libraries. The article also includes code samples and best practices for secure coding. You can read the article here.

6. XSS Filter Evasion Cheat Sheet

The XSS Filter Evasion Cheat Sheet provides a list of techniques that attackers use to bypass XSS filters. It also includes countermeasures that developers can use to prevent these attacks. The cheat sheet is regularly updated to include the latest evasion techniques and prevention strategies. You can find the cheat sheet here.