ZITADEL 3.0.0 through 3.4.15 and 4.0.0 before 4.19.5 contains a missing authorization vulnerability in Login V2 that allows attackers to approve OAuth 2.0 device authorizations using a victim's existing session without consent. Attackers can send a signed-in user a link carrying the attacker's user code to obtain the victim's tokens, and can bypass project access settings via the OIDC device authorization API.