dev.to· Oct 26, 2026· by rahibaly

Your JWT decodes fine — so why does the API still return 401?

Open Original Article ↗
You paste the token into a decoder, the header and payload look perfect, and the API still answers...
🎯 Vulnerability: OAuth 2.0 / JWT Authentication Bypass
💡 Defense Fix: Strictly verify JWT signatures on the backend, enforce state parameter validation, and reject 'alg: none'.
#webdev#security#javascript#tutorial