CVE-2026-19902: Ad Inserter <= 2.8.18 - Reflected Cross-Site Scripting via {search-query} Dynamic Tag (Referer Header)

Vulnerability summary

CVE-2026-19902 is a medium (CVSS 6.1) Cross-site Scripting vulnerability in spacetime ad inserter – ad manager & adsense ads. EPSS estimates a 0.26% chance of exploitation in the next 30 days, higher than 16.6% of scored vulnerabilities. Fixed in 2.8.19.

Timeline

1. 01-10-2026
   PublishedVulnerability first disclosed.
2. 03-10-2026
   Last modifiedVulnerability information updated.

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.

• CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.