Ninja Forms <= 3.8.4 is vulnerable to Subscriber+ Arbitrary Shortcode Execution vulnerability

The The Ninja Forms – The Contact Form Builder That Grows With You plugin for WordPress is vulnerable to arbitrary shortcode execution in all versions up to, and including, 3.8.4. 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.