RXSS Resolved On HackerOne - Undercode Testing

Reflected Cross-Site Scripting (RXSS) is a common web vulnerability where an attacker injects malicious scripts into a web application, which are then reflected back to the user’s browser. This can lead to session hijacking, defacement, or data theft. Recently, a researcher resolved an RXSS vulnerability on HackerOne, showcasing the importance of bug hunting and responsible disclosure.

Check the full writeup here:

https://lnkd.in/gddtj2uM

You Should Know:

1. How RXSS Works

RXSS occurs when user-supplied input is improperly sanitized and rendered in the browser. For example:

http://example.com/search?query=<script>alert(1)</script>

If the application reflects this input without encoding, the script executes.

2. Testing for RXSS

Use these payloads to test for RXSS:

<script>alert(document.domain)</script> 
<img src=x onerror=alert(1)>

3. Mitigation Techniques

Input Sanitization: Use libraries like DOMPurify.
Output Encoding: Encode special characters (<, >, &, etc.) before rendering.

Content Security Policy (CSP): Restrict script execution:

Content-Security-Policy: default-src 'self'; script-src 'unsafe-inline'

4. Linux Commands for Web Security Testing

Curl to Test Reflections:

curl -s "http://example.com/search?query=<script>alert(1)</script>" | grep -i "script"

Nikto for Web Scanning:
```
nikto -h example.com
```

OWASP ZAP for Automated Testing:

zap-cli quick-scan --self-contained http://example.com

5. Windows PowerShell for XSS Analysis

Invoke-WebRequest -Uri "http://example.com/search?query=<script>alert(1)</script>" | Select-String -Pattern "script"

What Undercode Say

RXSS remains a critical threat due to poor input handling. Always validate and sanitize user inputs. Use security headers like CSP and conduct regular penetration tests. Bug bounty platforms like HackerOne help improve security through community efforts.