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Vulnerability record · CVE-2026-33889 · published 15 April 2026

CVE-2026-33889: Apostrophecms cross-site scripting vulnerability

Apostrophecms · Apostrophecms

ApostropheCMS is an open-source Node.js content management system. Versions 4.28.0 and prior contain a stored cross-site scripting vulnerability in the @apostrophecms/color-field module, where color values prefixed with -- bypass TinyColor validation intended for CSS custom properties, and the launder.string() call performs only type coercion without stripping HTML metacharacters. These unsanitized values are then concatenated directly into <style> tags both in per-widget style elements rendered for all visitors and in the global stylesheet rendered for editors, with the output marked as safe HTML. An editor can inject a value which closes the style tag and executes arbitrary JavaScript in the browser of every visitor to any page containing the affected widget. This enables mass session hijacking, cookie theft, and privilege escalation to administrative control if an admin views draft content. This issue has been fixed in version 4.29.0.

5.4 CVSS 3.1 Medium EPSS 0.26% · top 84.6% CWE-79 · Cross-site scripting
5.4CVSS 3.1 base score
0.26%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
3References, 2 tagged exploit
17 Jun 2026Last modified by NVD

Description

ApostropheCMS is an open-source Node.js content management system. Versions 4.28.0 and prior contain a stored cross-site scripting vulnerability in the @apostrophecms/color-field module, where color values prefixed with -- bypass TinyColor validation intended for CSS custom properties, and the launder.string() call performs only type coercion without stripping HTML metacharacters. These unsanitized values are then concatenated directly into <style> tags both in per-widget style elements rendered for all visitors and in the global stylesheet rendered for editors, with the output marked as safe HTML. An editor can inject a value which closes the style tag and executes arbitrary JavaScript in the browser of every visitor to any page containing the affected widget. This enables mass session hijacking, cookie theft, and privilege escalation to administrative control if an admin views draft content. This issue has been fixed in version 4.29.0.

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/apostrophecms/apostrophe/commit/6a89bdb7acdb2e1e9bf1429961a6ba7f99410481 Patch
https://github.com/apostrophecms/apostrophe/security/advisories/GHSA-97v6-998m-fp4g ExploitMitigationVendor Advisory
https://github.com/apostrophecms/apostrophe/security/advisories/GHSA-97v6-998m-fp4g ExploitMitigationVendor Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2026-33889), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.