CVE-2026-16779: Kubio AI Page Builder <= 2.8.5 - Missing Authorization to Authenticated (Contributor+) Front-Page/Menu/Template Configuration Reversion via kubio_restore_front_page AJAX Action

The Kubio AI Page Builder plugin for WordPress is vulnerable to authorization bypass in all versions up to, and including, 2.8.5. This is due to the plugin not properly verifying that a user is authorized to perform an action. This makes it possible for authenticated attackers, with contributor-level access and above, to overwrite front-page configuration options (showonfront, pageonfront, and pageforposts), rewrite primary navigation menu items, replace template parts, and overwrite the Kubio global-data post. Although a nonce check via checkajaxreferer() is present, the nonce is unconditionally emitted into window.kubioUtilsData for every user who can load the block editor, making it harvestable by any Contributor and therefore an ineffective authorization barrier.