Privilege escalation in Mobile builder plugin for WordPress

The Mobile builder plugin for WordPress is vulnerable to Privilege Escalation in all versions up to, and including, 1.4.2 via the `wcfmmp_profile_settings()` REST handler exposed at `POST /mobile-builder/v1/wcfm-profile-settings`. This is due to a PHP loose-comparison logic flaw in the meta key allow-list check — `strpos( $key, 'mobile_builder' ) == 0` evaluates to `true` for any key that does *not* contain the substring `'mobile_builder'` because `strpos()` returns `false` on no match and `false == 0` is `true` in PHP — combined with a `permission_callback` (`user_permissions_check`) that grants access to any authenticated user by only verifying `$user->exists()`. This makes it possible for authenticated attackers, with Subscriber-level access and above, to pass an unsanitized `data` array via the `key` and `data` parameters directly to `update_user_meta()`, overwriting arbitrary user meta on their own account — including the `wp_capabilities` meta key — to grant themselves Administrator-level privileges.