We Were Hitting Auth0 /userinfo on Every Request. Here's the Fix.
Our backend hit Auth0's /userinfo as a fallback for missing JWT claims — thousands of external calls per day. The right fix was on the Auth0 side.
🎯 Vulnerability: OAuth 2.0 / JWT Authentication Bypass
💡 Defense Fix: Strictly verify JWT signatures on the backend, enforce state parameter validation, and reject 'alg: none'.