Advanced Country Blocker <= 2.3.1 - Unauthenticated Authorization Bypass via Insecure Default Secret Key

The Advanced Country Blocker plugin for WordPress is vulnerable to Authorization Bypass in all versions up to, and including, 2.3.1 due to the use of a predictable default value for the secret bypass key created during installation without requiring users to change it. This makes it possible for unauthenticated attackers to bypass the geolocation blocking mechanism by appending the key to any URL on sites where the administrator has not changed the default value.