Does input validation prevent XSS?
Not alone. A valid string can still contain script tags. Validation limits the surface (rejects too-long fields, enforces types), but you also need to escape on render and strip HTML from input. Layer defenses; no single fix is enough.
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More FAQs in How to Prevent XSS in Node.js Applications
Cross-Site Scripting. An attacker submits malicious HTML or JavaScript to your app. When another user views it, the script runs in their browser. Can steal sessions, deface the app, or spread worms.
Escape output (React does this by default), strip HTML from input with xss-clean or dompurify, use httpOnly cookies, set a Content Security Policy with helmet, validate input, and sanitize rich text on render. Layer defenses.
If a script does run in the browser, it cannot read httpOnly cookies. The JWT token stored in an httpOnly cookie is safe. This is defense in depth; it does not prevent XSS, but limits the damage.
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