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 doesn't sufficiently enforce the second factor for authentication providers that authenticate every request on their own. An attacker who knows the password of an account with two-factor authentication enabled can use that account's permissions through routes that accept such a provider, without providing the second factor. This vulnerability is mitigated by the fact that the attacker must know the account's password, a per-request authentication provider (such as the the HTTP Basic Authentication module) must be enabled, and an alternate authentication method (such as JSON:API or REST) must be enabled.