The WP 2FA – Two-factor authentication for WordPress plugin for WordPress is vulnerable to Cross-Site Request Forgery in all versions up to, and including, 2.5.0. This is due to missing or incorrect nonce validation on the send_backup_codes_email function. This makes it possible for unauthenticated attackers to send emails with arbitrary content to registered users via a forged request granted they can trick a site administrator or other registered user into performing an action such as clicking on a link. While a nonce check is present, it is only executed if a nonce is set. By omitting a nonce from the request, the check can be bypassed.
The web application does not, or cannot, sufficiently verify whether a request was intentionally provided by the user who sent the request, which could have originated from an unauthorized actor.