This module enables you to require a second authentication factor (a time-based one-time password from an authenticator app) when users log in. The module does not enforce the second authentication factor correctly. As a result, an attacker who has only the first factor for an account with 2FA (for example, a valid one-time login link) could trigger actions that should only follow a fully authenticated login. These include updating the account's last login time, (which also invalidates other one-time login links) and running other modules' login hooks. The vulnerability is mitigated by the fact that the attacker must already have the account's first factor (a valid one-time login link, or a login through another module), and the impact depends on which other modules react to user logins.