Capgo (capgo.app) fails to restrict direct write access to the public.ssoproviders table exposed through Supabase PostgREST. A holder of an ordinary Capgo full API key can insert a row with status='active' and enforcesso=true, bypassing the intended backend SSO provisioning route (supabase/functions/backend/private/sso/providers.ts) and its controls: the Enterprise plan requirement, SSO provider creation via the Supabase Management API, DNS TXT domain-ownership verification, the pendingverification → verified → active status transition, and issuance of a trusted provider ID by Supabase Auth. The forged row is trusted by SSO discovery and enforcement logic, including the unauthenticated login preflight endpoint /private/sso/check-domain, which then reports {"hassso": true, "enforcesso": true} for domains that were never verified, allowing attacker-controlled SSO enforcement to be asserted for arbitrary domains and disrupting normal login. All versions are affected; at the time of the advisory no patch was available.