WP 2FA with Telegram <= 3.0 - Authenticated (Subscriber+) Authentication Bypass

The WP 2FA with Telegram plugin for WordPress is vulnerable to Authentication Bypass in versions up to, and including, 3.0. This is due to insufficient validation of the user-controlled key on the 'validate_tg' action. This makes it possible for authenticated attackers, with subscriber-level permissions and above, to log in as any existing user on the site, such as an administrator.