Add Hierarchy (parent) to post <= 3.12 - Reflected Cross-Site Scripting

The Add Hierarchy plugin for WordPress is vulnerable to Reflected Cross-Site Scripting in versions up to, and including, 3.12 due to the use of add_query_arg/remove_query_arg with insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages via a URL that executes if they can successfully trick a user into performing an action such as clicking on a link.