CVE-2026-53608: Apostrophecms @apostrophecms/seo

High severity, CVSS 8.7. EPSS: 0.4% chance of exploitation in the next 30 days.

ApostropheCMS is an open-source Node.js content management system. Versions up to and including 1.4.2 of the `@apostrophecms/seo` package injects the Google Analytics Tracking ID (`seoGoogleTrackingId`) and Google Tag Manager ID (`seoGoogleTagManager`) directly into `<script>` tag bodies using JavaScript template literals without any sanitization or validation. Any user with editor-level access (the default role for content managers) can set these fields to a malicious value, resulting in stored XSS that executes on every page for every visitor of the site. As of time of publication, no known patched versions are available.

Affected products

• Apostrophecms @apostrophecms/seo: up to and including 1.4.2

Published 2026-06-12. Last modified 2026-06-17.