phpMyFAQ's two-factor authentication login bypasses the password factor

phpMyFAQ is an open source FAQ web application. Versions 3.2.0 through 4.1.5 contain an authentication bypass in its public two-factor authentication verification flow: an unauthenticated attacker can submit an account’s numeric user ID and a valid or brute-forced six-digit TOTP code without first authenticating with the account password, allowing takeover of any 2FA-enabled account, including administrator accounts. Version 4.1.6 is patched by binding TOTP verification to a session established after successful password authentication and limiting failed TOTP attempts. No official workaround is documented; affected installations should upgrade to 4.1.6 or later.