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Vulnerabilities

Security fix · CVE-2026-112958

ApostropheCMS is an open-source Node.js content management system.

Published Oct 20, 2026 · catalog updated Oct 21, 2026 · ApostropheCMS is an open-source

Last checked Nov 3, 2026. A connected source was read within the last 7 days.

Check if you run it

No confirmed exploitation is on record for CVE-2026-112958. EPSS is 0.30%. Act only if a listed version of ApostropheCMS is an open-source is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (ApostropheCMS is an open-source).
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
Medium5.4
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.30%
Remediation
Version ranges on file
Affected products
npm apostrophe

## Summary ApostropheCMS widget styles support project-defined schema fields. If a project defines a free-form style field with a CSS and no selector, an editor-controlled value is rendered as an inline CSS declaration. The resulting declaration is then inserted into the widget wrapper's attribute without HTML-attribute escaping. An attacker who can edit the widget can include a double quote in the style value, terminate the attribute, and inject new HTML event-handler attributes. The payload is stored with the widget and executes in the Apostrophe site origin whenever the affected published page is rendered. This is a sibling of CVE-2026-33889 / . The earlier issue escaped from a element through a malicious color value. This variant reaches a different sink related to the automatically generated widget wrapper's inline and attributes. ## Details ### Root Cause 1: Free-form string style values retain HTML metacharacters The standard string field converter uses and length validation. This performs type normalization, not output encoding for an HTML attribute context: [ ](https://github.com/apostrophecms/apostrophe/blob/aa5170c7df9ff9ea5ac2e72a008f12e28dae6ca8/packages/apostrophe/modules/%40apostrophecms/schema/lib/addFieldTypes.js#L296-L333) Quotes therefore remain in a value supplied through a style field. ### Root Cause 2: The value is converted into inline CSS without value validation For a field with but no or media query, selects inline rendering. The generic extractor concatenates the configured property and editor-controlled value: [ ](https://github.com/apostrophecms/apostrophe/blob/aa5170c7df9ff9ea5ac2e72a008f12e28dae6ca8/packages/apostrophe/modules/%40apostrophecms/styles/ui/apos/universal/render.mjs#L171-L228) [ ](https://github.com/apostrophecms/apostrophe/blob/aa5170c7df9ff9ea5ac2e72a008f12e28dae6ca8/packages/apostrophe/modules/%40apostrophecms/styles/ui/apos/universal/render.mjs#L598-L647) For example, the value below becomes part of a declaration: ###

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • npm apostrophe< 4.34.0

How to fix CVE-2026-112958

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-112958. EPSS is 0.30%. Act only if a listed version of ApostropheCMS is an open-source is installed.

Which versions are affected?

Compare what you have installed with < 4.34.0. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-79: Cross-site Scripting (XSS). EPSS 0.30%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Oct 20, 2026 · NIST NVD

    Detected

    ApostropheCMS is an open-source Node.js content management system. Prior to 4.34.0, a project-defined free-form widget style field can carry an editor-controlled quote into an inline style attribute because the wrapper serializer does not apply HTML-attribute encoding. The quote can terminate the style attribute and inject executable attributes when published content, or an affected draft viewed b

  2. Oct 20, 2026 · NIST NVD

    Updated

    ApostropheCMS is an open-source Node.js content management system. Prior to 4.34.0, a project-defined free-form widget style field can carry an editor-controlled quote into an inline style attribute because the wrapper serializer does not apply HTML-attribute encoding. The quote can terminate the style attribute and inject executable attributes when published content, or an affected draft viewed b

  3. Oct 21, 2026 · GitHub Advisory Database

    Updated

    ## Summary ApostropheCMS widget styles support project-defined schema fields. If a project defines a free-form style field with a CSS and no selector, an editor-controlled value is rendered as an inline CSS declaration. The resulting declaration is then inserted into the widget wrapper's attribute without HTML-attribute escaping. An attacker who can edit the widget can include a double quote in th

Sources

  • CVE.orgVulnerability recordCVE-2026-112958

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-112958

    30-day exploitation probability 0.30%

    first.org
  • GitHub Advisory DatabasePackage advisoryGHSA-7jg5-frgc-c67w

    ApostropheCMS: Stored XSS via Unescaped Widget Style Attribute Serialization

    github.com
  • GitLab Advisory DatabasePackage advisoryCVE-2026-112958

    ApostropheCMS widget styles support project-defined schema fields. If a project defines a free-form string style field with a CSS property and no selector, an editor-controlled value is rendered as an inline CSS declaration. The resulting declaration is then inserted into the widget wrapper's style="&hellip;" attribute without HTML-attribute escaping. An attacker who can edit the widget can includ

    advisories.gitlab.com
  • NIST NVDVulnerability recordCVE-2026-112958

    ApostropheCMS is an open-source Node.js content management system. Prior to 4.34.0, a project-defined free-form widget style field can carry an editor-controlled quote into an inline style attribute because the wrapper serializer does not apply HTML-attribute encoding. The quote

    nvd.nist.gov

References

Freshness

Last verified in this catalog Nov 3, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • FIRST EPSSNov 3, 2026
  • GitLab Advisory DatabaseOct 23, 2026
  • GitHub Advisory DatabaseOct 22, 2026
  • CVE.orgOct 21, 2026
  • NIST NVDOct 21, 2026