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Last updated: May 1, 2026
Why this module exists. OAuth 2.0 and OIDC are the universal authentication layer of the modern web — and the most-misunderstood spec in the industry. The protocol is fine; the implementations are catastrophic.
Why this module exists. OAuth 2.0 and OIDC are the universal authentication layer of the modern web — and the most-misunderstood spec in the industry. The protocol is fine; the implementations are catastrophic. “Sign in with Google”, “Sign in with Apple”, “Sign in with Facebook” — every one of these has had account-takeover bugs in the last 5 years.
The protocol in 30 seconds
- User clicks “Sign in with Google” on app.example.com.
- App.example.com redirects user to Google with parameters:
client_id,redirect_uri,state,scope,response_type. - Google authenticates the user, asks for consent.
- Google redirects back to
redirect_uriwith an authorizationcode+ thestatethe app sent. - App.example.com exchanges the code (server-to-server) for an access token + ID token.
- App parses the ID token to get the user identity, creates a session.
Every step has bugs in the wild.
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