Why OAuth: delegation, not authentication

Welcome to OAuth 2.0 / OIDC & Federated Identity — the first pillar of the Security discipline's Authentication & Identity domain. OAuth is how one app gets delegated access to your account somewhere else without your password. This track drives the authorization-code flow — the backbone of modern sign-in — and the two checks that keep it safe.

Same thread as every module here: concept → protocol → attack → defence. The graded work is always the defence — here, rejecting a tampered state (the check that stops cross-site request forgery, CSRF — another site submitting the flow for you) and an unregistered redirect_uri (open redirect).

The code runs entirely in your browser (Pyodide); nothing leaves your machine.