Unauthenticated DCR previously accepted any redirect_uri; combined with the
auto-approving /consent handler an attacker could register a client pointing at
their domain, phish a logged-in user, and silently receive an auth code for the
victim's identity. Reject non-allowlisted redirect_uri hosts at registration
(default: claude.ai, claude.com, and the BETTER_AUTH_URL/portal host).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Chris Farhood