Broken Link Checker <= 2.4.14.1 - Unauthenticated Arbitrary Shortcode Execution via parser_callback

The The Broken Link Checker plugin for WordPress is vulnerable to arbitrary shortcode execution in all versions up to, and including, 2.4.14.1. 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. Exploitation requires that a submitted comment containing the shortcode payload in an href or src attribute is approved through the site's normal comment moderation workflow; once approved, the shortcode is executed automatically via WP-Cron without any further attacker interaction.