CVE-2026-55834: Pocket-ID has an Open Redirect on the OIDC /authorize page via unvalidated redirect_uri with prompt=none

The OIDC authorization page in the pocket-id frontend redirects the browser to an attacker-controlled URL without consulting the backend redirect_uri allow-list when the request uses prompt=none. An attacker who knows a valid client_id can craft an /authorize link that sends a victim (or a victim’s browser doing a silent re-auth) to any external https URL, enabling phishing and OAuth response smuggling. The backend allow-list validation that protects the normal authenticated flow is bypassed because this path is handled entirely client-side.