WCK WordPress plugin: authenticated users can read private post custom fields

Custom Post Types and Custom Fields creator (WCK) before 2.4.1 contains a missing authorization vulnerability that allows authenticated attackers with access to any WCK meta box to read custom-field values on posts they cannot edit by exploiting the wck_show_update_form AJAX handler, which lacks the capability checks enforced by other handlers and relies on a shared, non-unique nonce action. Attackers can send a crafted admin-ajax.php request with a valid wck-edit-entry nonce, a target meta key, and an arbitrary post ID to disclose sensitive post-meta or option values belonging to other users, including private or draft post data.