XSS CSRF Prevention Advanced

Cross-site scripting (XSS) and cross-site request forgery (CSRF) are the two most common web vulnerabilities. XSS allows attackers to inject and execute arbitrary JavaScript in a victim's browser, stealing session cookies, credentials, or performing actions on behalf of the user. CSRF tricks an authenticated user into making unwanted requests to another application where they're logged in, without their knowledge or consent. Advanced prevention goes beyond simple input filtering. It requires layered defenses: Content Security Policy (CSP) headers, output encoding context-awareness, SameSite cookie flags, CSRF token validation, origin checking, and secure redirect handling. The field encompasses threat modeling, browser security models, and architectural decisions that span backend and frontend.