Break Filter JS From HTML

Overview

This skill provides a systematic methodology for analyzing and bypassing HTML sanitization filters that attempt to prevent JavaScript execution. The focus is on understanding filter mechanics deeply before attempting bypasses, and on robust verification of solutions.

When to Use This Skill

• Analyzing HTML sanitization filters to find bypass vectors
• CTF challenges involving XSS filter evasion
• Authorized security testing of web application input sanitization
• Understanding parser differentials between server-side parsers and browsers

Phase 1: Environment and Filter Analysis

Before attempting any bypass, thoroughly understand the test environment and filter mechanics.

Environment Reconnaissance