Capgo - Account Merge via Poisoned public.users.email in SSO Provisioning

Capgo before 12.128.12 allows authenticated users to modify their mutable public.users.email to arbitrary addresses, which the SSO provisioning endpoint trusts as an account-merge key. Attackers can pre-position their account with a victim's corporate SSO email, causing the provision-user endpoint to merge the victim's SSO identity into the attacker-controlled account.