@apostrophecms/seo Vulnerable to Stored XSS via Unsanitized Google Analytics / GTM ID Injected into Script Tag

published 2026-06-12 4 mo ago modified 2026-10-25 14 d ago also GHSA-wf43-fpp3-cf65 , EUVD-2026-36589

cvss: 8.7; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.3%; EPSS 0.3% chance of exploitation in 30 days, percentile 17%
public exploits: 0; none known

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.

Patch / fix

fixed in 1 links 2

npm @apostrophecms/seo 1.5.0

github.com/apostrophecms/apostrophe@5a88e96 commit
github.com/apostrophecms/apostrophe#5464 pull request

CISA SSVC

Exploitation: Proof of concept is public
Automatable: no
Technical impact: total
Assessed: 4 mo ago (2026-06-15)

Exploit prediction

0.26% chance of exploitation in the next 30 days, higher than 17% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

github.com https://github.com/apostrophecms/apostrophe/security/advisories/GHSA-wf43-fpp3-cf65 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
CNA	3.1	8.7	CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N
GitHub	3.1	8.7	CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N

Affected packages

ecosystem	package	affected	fixed in
npm	@apostrophecms/seo	<1.5.0	1.5.0

Affected products

apostrophecms @apostrophecms/seo

Classification

Weakness

CWE-79 Improper Neutralization of Input During Web Page Generation

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary