Finding Cross-Site Scripting (XSS) vulnerabilities in Bug bounty program

Finding XSS in Bug bounty program can be hard at first, so I have wrote some things together to do have a roadmap whenever doing bug bounty.

1. Input Vectors:

URL Parameters: These are parts of the URL that can be manipulated. For example, http://example.com/page?name=John — test by injecting scripts into name.Form Inputs: Fields where users enter data, such as login forms, search bars, and comments.HTTP Headers: Headers like User-Agent or Referer can sometimes be manipulated to execute scripts.Cookies: If cookies are improperly handled, they might be another vector for XSS.

2. Payloads:

Basic Payloads: Start with simple scripts like <script>alert('XSS')</script>.Advanced Payloads: Use variations to bypass filters, such as "><script>alert('XSS')</script> or SRC=javascript:alert('XSS').Polyglots: These are payloads that can execute in multiple contexts, e.g., "><img src=x onerror=alert(1)>.

3. Bypassing Filters:

Encoding: Use HTML entity encoding (e.g., &lt;script&gt;) or URL encoding (%3Cscript%3E).Nested Encoding: Double or triple encode to bypass simple filters.Case Variations: Change the case of tags or attributes, e.g., <ScRipT>.

4. Testing Strategies:

Fuzzing: Input random data into fields to see how the application processes it.Contextual Testing: Understand the context (HTML, JavaScript, CSS) where your input is reflected and craft your scripts accordingly.DOM Analysis: Use browser developer tools to inspect the Document Object Model (DOM) and identify client-side vulnerabilities.

5. Tools and Automation:

Burp Suite: A comprehensive tool that allows for manual and automated testing of web applications.OWASP ZAP: An open-source web application security scanner.XSSer: A tool specifically designed to find XSS vulnerabilities.Browser Extensions: Extensions like “XSS Rays” for Chrome can help in manual testing.

6. Reporting:

Detailed Reports: Provide step-by-step details, including the exact payload used, screenshots, and how the vulnerability can be reproduced.Impact Explanation: Explain the potential impact of the vulnerability, such as data theft or session hijacking.Mitigation Suggestions: Offer guidance on how to fix the vulnerability, like input validation and output encoding.Stay Legal: Only test applications that are part of a bug bounty program and have given explicit permission.Continuous Learning: The cybersecurity field evolves rapidly, so keep learning about new techniques and vulnerabilities.Engage with the Community: Join forums, attend workshops, and participate in Capture The Flag (CTF) competitions to improve your skills.