CVE-2026-3339: Improper Limitation of a Pathname to a Restricted Directory

The Keep Backup Daily plugin for WordPress is vulnerable to Limited Path Traversal in all versions up to, and including, 2.1.1 via the `kbd_open_upload_dir` AJAX action. This is due to insufficient validation of the `kbd_path` parameter, which is only sanitized with `sanitize_text_field()` - a function that does not strip path traversal sequences. This makes it possible for authenticated attackers, with Administrator-level access and above, to list the contents of arbitrary directories on the server outside of the intended uploads directory.