# Cross-Site Scripting (XSS)
Confidence: high
Last verified: 2026-05-22
Generation: human_only


## TL;DR

XSS is an injection attack where malicious scripts are injected into trusted websites, executing in victims' browsers. Three types: Stored (persistent, in database), Reflected (in URL parameters), DOM-based (client-side JavaScript vulnerability). Prevention: output encoding, Content Security Policy (CSP), input validation.

## Core Explanation

Reflected XSS: attacker crafts URL with script in query parameter, victim clicks link, script executes in victim's context. Stored XSS: script stored in database (comment, profile), executed whenever any user views the page. DOM XSS: client-side code writes user input to innerHTML without sanitization. Modern frameworks (React/Vue/Angular) auto-escape by default, reducing but not eliminating risk.

## Further Reading

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