InPost Gallery <= 2.1.4.2 - Authenticated (Subscriber+) Arbitrary Shortcode Execution via inpost_gallery_get_shortcode_template

The The InPost Gallery plugin for WordPress is vulnerable to arbitrary shortcode execution via the inpost_gallery_get_shortcode_template AJAX action in all versions up to, and including, 2.1.4.2. 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 authenticated attackers, with Subscriber-level access and above, to execute arbitrary shortcodes.