Cap-go before 12.128.2 contains an authentication logic flaw that lets an attacker register and control an account bound to a victim's email address before that email is verified. By enabling two-factor authentication on the pre-registered account, the attacker gains control over the account claimed under the victim's identity, allowing them to read and modify its state and enforce organization-level policies, while the legitimate user is denied access to the account tied to their own email.