The The WP Photo Album Plus plugin for WordPress is vulnerable to arbitrary shortcode execution via getshortcodedrenderedfenodelay AJAX action in all versions up to, and including, 8.8.08.007 . This is due to the software allowing users to execute an action that does not properly validate a value before running do_shortcode. This makes it possible for unauthenticated attackers to execute arbitrary shortcodes.
https://wordpress.org/plugins/wp-photo-album-plus/#developers
https://plugins.trac.wordpress.org/changeset/3184852/
https://plugins.trac.wordpress.org/browser/wp-photo-album-plus/tags/8.8.08.004/wppa-ajax.php#L1238