XSS Prevention Guide: Escaping, CSP, and Trusted Types
How cross-site scripting works, the three XSS types, output encoding rules per context, and how CSP provides a defense-in-depth layer.
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Tags: security, web, xss
XSS Prevention: Output Encoding, CSP, and DOMPurify Cross-Site Scripting (XSS) is one of the most prevalent web vulnerabilities. It occurs when an attacker's script is executed in the context of a victim's browser session, allowing session theft, page modification, keylogging, and data exfiltration. Unlike SQL injection (one context, one fix), XSS has multiple contexts — each requiring a different encoding strategy. The Three Types of XSS Stored XSS: Malicious content is saved to the database and served to all users who view it. A comment containing stored in a forum, rendered to every visitor. Reflected XSS: Malicious content is in the URL and reflected in the response. The victim is tricked into clicking a crafted link. DOM XSS: The vulnerability is in client-side JavaScript that reads…
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