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.

Requests carrying this pattern arrive without a session, so nothing upstream of the firewall gets a chance to reject them: WordSec's web application firewall inspects request payloads before WordPress loads them. Classes like this one can leave something behind, so the staged malware scanner is the second half: it looks for dropped files and modified code rather than for the request that created them. None of that substitutes for the fix: Broken Link Checker 2.4.15 closes this, and updating the plugin is the step that ends it.

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