The Ad Inserter – Ad Manager & AdSense Ads plugin for WordPress is vulnerable to Reflected…

Why it is Yellow

• CVSS 6.1 medium

References

• https://plugins.trac.wordpress.org/browser/ad-inserter/tags/2.8.18/ad-inserter.php#L13018
• https://plugins.trac.wordpress.org/browser/ad-inserter/tags/2.8.18/ad-inserter.php#L13022
• https://plugins.trac.wordpress.org/browser/ad-inserter/tags/2.8.18/ad-inserter.php#L13025
• https://plugins.trac.wordpress.org/browser/ad-inserter/tags/2.8.18/ad-inserter.php#L13093
• https://plugins.trac.wordpress.org/browser/ad-inserter/tags/2.8.18/class.php#L3297
• https://plugins.trac.wordpress.org/changeset/3709957/ad-inserter/trunk/ad-inserter.php
• https://plugins.trac.wordpress.org/changeset?reponame=&new=3709970%40ad-inserter%2Ftags%2F2.8.19&old=3624916%40ad-inserter%2Ftags%2F2.8.18
• https://www.wordfence.com/threat-intel/vulnerabilities/id/5d632cce-40a9-4969-b213-8370ae75287e?source=cve

Original description

The Ad Inserter – Ad Manager & AdSense Ads plugin for WordPress is vulnerable to Reflected Cross-Site Scripting via the Referer header in all versions up to, and including, 2.8.18 due to insufficient input sanitization and output escaping on the '{search-query}' dynamic tag. When an ad block's code contains that tag, replace_ai_tags() reads $_SERVER['HTTP_REFERER'] and tests it with the regex /[\.\/](google|yahoo|bing|ask)\.[a-z\.]{2,5}[\/]/i. The leading [\.\/] class matches a literal slash, so any referrer merely containing a segment such as '/google.com/' passes as a search-engine referral; the plugin then percent-decodes the referring query with parse_str() and substitutes the resulting 'q' (or 'p') value into the block via preg_replace() with no escaping. This makes it possible for unauthenticated attackers to execute arbitrary JavaScript in the context of the site for any visitor, including a signed-in administrator, by luring them to an attacker-controlled page that frames or links to any ordinary post. Exploitation requires the site to have an ad block whose code uses the '{search-query}' tag with automatic insertion enabled — a documented plugin feature used as intended.