The Contest Gallery plugin for WordPress is vulnerable to authorization bypass in all versions up to, and including, 28.0.2. This is due to the plugin registering the cg_check_wp_admin_upload_v10 AJAX action for both authenticated and unauthenticated users without implementing capability checks or nonce verification. This makes it possible for unauthenticated attackers to inject arbitrary WordPress media attachments into galleries and manipulate gallery metadata via the cg_check_wp_admin_upload_v10 action. It does not enable an attacker to move or upload files.