XSS Checker

What is XSS?

XSS (Cross-Site Scripting) is a security vulnerability that allows attackers to inject malicious scripts into web pages viewed by other users. XSS attacks occur when user input is not properly validated or sanitized before being rendered in the browser. This can lead to session hijacking, data theft, and unauthorized actions.

Our free XSS Checker tests input for common XSS patterns. It detects script tags, event handlers, and other potentially dangerous patterns. Note that this is a basic client-side check. Comprehensive XSS testing requires server-side validation and proper security testing tools.

Types of XSS

• Stored XSS: Malicious script stored on server (database, comments)
• Reflected XSS: Malicious script reflected in response (URL parameters)
• DOM-based XSS: Vulnerability in client-side JavaScript

Common XSS Payloads

• <script>alert('XSS')</script>
• <img src=x onerror=alert('XSS')>
• <svg onload=alert('XSS')>
• javascript:alert('XSS')

Prevention

• Input Validation: Validate and sanitize all user input
• Output Encoding: Encode output before rendering
• Content Security Policy: Use CSP headers
• Use Frameworks: Use frameworks with built-in XSS protection

FAQs

What is XSS used for?

XSS is a security vulnerability that allows attackers to execute malicious scripts in users' browsers, potentially stealing data or performing unauthorized actions.

How do I prevent XSS?

Validate and sanitize all user input, encode output before rendering, use Content Security Policy, and use frameworks with built-in protection.

Is XSS testing legal?

Only test XSS vulnerabilities on systems you own or have explicit permission to test. Unauthorized testing is illegal.

What is Content Security Policy?

CSP is a security feature that helps prevent XSS by controlling which resources can be loaded and executed on a page.