GHSA-xr8f-h2gw-9xh6 OAuth 2.1 Provider: Unprivileged users can register OAuth clients

• npm @better-auth/oauth-provider: >= 1.4.8-beta.7, < 1.6.5 → fixed in 1.6.5 • npm @better-auth/oauth-provider: >= 1.7.0-beta.0, <= 1.7.0-beta.1 (no fix yet)

Am I affected? You're affected if all of the following are true: • Using @better-auth/oauth-provider at version specified below • You configured clientPrivileges in the plugin options expecting it to gate who can create OAuth clients • The /oauth2/create-client or /admin/oauth2/create-client endpoints are reachable by authenticated users you don't fully trust If clientPrivileges is not configured, this bug has no security consequence for your deployment --- ### Summary The clientPrivileges option documents a create action, but the OAuth client creation endpoints did not invoke the hook before persisting new clients. Deployments that configured clientPrivileges to restrict client registration were not actually restricted — any authenticated user could reach the create endpoints and register an OAuth client with attacker-chosen redirect URIs and metadata. Non-create operations (read, list, update, delete, rotate) enforced the hook correctly. Only the create path was missing the check. Impact • Unauthorized registration of OAuth clients by any authenticated user, under deployments that expected clientPrivileges to block them. • Attacker-controlled redirect_uris on those clients enable phishing flows that present as registered first-party applications. • If the SERVER_ONLY admin creation endpoint is also exposed to low-privilege users (a separate deployment misconfiguration), additional sensitive fields including `skip_consent` become writable. Patches Fixed in `@better-auth/[email protected]` Both create endpoints now call the clientPrivileges hook with action "create" before persisting the client record. Workarounds If you cannot upgrade immediately: • Block the /oauth2/create-client and /admin/oauth2/create-client routes at your reverse proxy or middleware layer for any user who should not be able to register clients. • Do not expose the admin creation endpoint (it is SERVER_ONLY by design and should not be reachable by end-user sessions).