CVE-2026-92161: FriendsOfFlarum OAuth: Unauthenticated account takeover via unverified email trust in Discord OAuth provider

An unauthenticated account takeover vulnerability exists in fof/oauth when the Discord OAuth provider is enabled.

Discord allows an account to use an unverified email address when its phone number has been verified. During OAuth authentication, Discord may return that email address with "verified": false.

Affected versions of fof/oauth did not validate this flag and passed the email address to Flarum core as trusted via provideTrustedEmail(). Flarum core could then match the trusted email address to an existing user, link the attacker-controlled Discord identity to that user, and authenticate the attacker as the victim.

An attacker who knows a user’s email address can therefore take over the corresponding Flarum account without knowing its password or requiring any interaction from the victim. This includes administrator accounts.