The document discusses techniques for protecting web applications from client-side attacks using JavaScript (Waf.js). It covers the following key points in 3 sentences: Waf.js provides defenses like CSRF prevention, DOM-based XSS prevention, and detection of unwanted applications. It utilizes parsers like Acorn and DOMPurify to parse and sanitize inputs to prevent injections. The document outlines approaches used by Waf.js to build the AST of an input and search for dangerous code like function calls to prevent attacks while minimizing false positives.