Backup Migration <= 2.0.0 - Missing Authorization to Unauthenticated Backup Upload to Offline Storage

The Backup Migration plugin for WordPress is vulnerable to Missing Authorization in all versions up to, and including, 2.0.0. This is due to a missing capability check on the 'initializeOfflineAjax' function and lack of proper nonce verification. The endpoint only validates against hardcoded tokens which are publicly exposed in the plugin's JavaScript. This makes it possible for unauthenticated attackers to trigger the backup upload queue processing, potentially causing unexpected backup transfers to configured cloud storage targets and resource exhaustion.