A critical vulnerability exists in the Simple Membership WordPress plugin before version 4.7.8. The plugin fails to verify whether user creation succeeded during registration before using the returned value as a user ID to update an account. This logic flaw allows unauthenticated attackers to overwrite the primary administrator's account data, including the email address. By replacing the admin email, attackers can then trigger a password reset to gain full control of the administrator account. The attack requires no authentication, making it particularly dangerous for any site running the affected plugin version. Sites should upgrade to version 4.7.8 or later immediately to remediate the vulnerability.