The Broken Link Checker plugin for WordPress is vulnerable to Reflected Cross-Site Scripting due to the use of add_query_arg in /app/admin-notices/features/class-view.php without appropriate escaping on the URL in all versions up to, and including, 2.4.0. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that execute if they can successfully trick a user into performing an action such as clicking on a link.
The product receives input from an upstream component, but it does not neutralize or incorrectly neutralizes special characters such as "<", ">", and "&" that could be interpreted as web-scripting elements when they are sent to a downstream component that processes web pages.