mutation-xss-anti-pattern

What problem does it solve?

This Skill addresses the critical security vulnerability of Mutation XSS (mXSS), which bypasses standard HTML sanitizers by exploiting inconsistencies in how browsers parse malformed HTML.

Core Features & Use Cases

• Detect mXSS Vulnerabilities: Identifies instances where HTML sanitizers fail to account for browser parsing quirks, leading to script execution.
• Promote Secure Sanitization: Guides users towards using robust, mutation-aware sanitization libraries like DOMPurify.
• Defense-in-Depth: Emphasizes the importance of Content Security Policy (CSP) as a secondary defense.
• Use Case: Reviewing a web application's comment section or rich text editor to ensure user-submitted HTML is safely rendered without executing malicious scripts, even if the HTML is intentionally malformed to trick the sanitizer.

Quick Start

Review the provided HTML snippet for potential mutation XSS vulnerabilities using a secure sanitization approach.