CVE-2026-112951: ApostropheCMS: Color field validation bypass allows stored XSS via HTML appended after rgb()/hsl() prefix

Q: Who can exploit this issue?

An authenticated ApostropheCMS user with edit rights can exploit it. Exploitation also requires a victim to render content containing the malicious stored color value.

Q: Are default color-field deployments affected?

The issue affects ApostropheCMS versions prior to 4.34.0 where the color field accepts a value with a valid rgb() or hsl() prefix followed by trailing HTML. The provided data does not identify any configuration requirement beyond use of the affected color field.

Q: How can I determine whether content may already be malicious?

Review stored color-field values for entries that begin with rgb() or hsl() but contain additional trailing HTML or other unexpected content. Such values may have bypassed validation and execute when rendered.

Q: What is the remediation?

Upgrade ApostropheCMS to version 4.34.0, which fixes the validation issue. If an upgrade is not immediately possible, restrict edit access to trusted users and inspect stored color-field values for trailing content.

Published Oct 20, 2026

Updated

ApostropheCMS is an open-source Node.js content management system. Prior to 4.34.0, the color field accepts trailing content after a valid rgb() or hsl() prefix because its TinyColor validation does not require the entire value to match a color. An authenticated user with edit rights can store arbitrary HTML after a valid color prefix. When the stored value is rendered, the payload executes, resulting in stored XSS. This issue is fixed in version 4.34.0.

Affected Software

1 affected component

Apostrophe Technologies ApostropheCMS<4.34.0

Remediation

Recommended actions to resolve this vulnerability, in priority order.

Upgrade
Upgrade ApostropheCMS to a version that resolves this vulnerability.
Fixed in 4.34.0

Event History

Oct 20, 2026

CVE Published

via MITRE·03:33 PM

Data Sourced

via MITRE·03:33 PM

DescriptionSeverityWeakness

Data Sourced

via NVD·04:17 PM

DescriptionSeverityWeakness

Frequently Asked Questions

Who can exploit this issue?

An authenticated ApostropheCMS user with edit rights can exploit it. Exploitation also requires a victim to render content containing the malicious stored color value.

Are default color-field deployments affected?

The issue affects ApostropheCMS versions prior to 4.34.0 where the color field accepts a value with a valid rgb() or hsl() prefix followed by trailing HTML. The provided data does not identify any configuration requirement beyond use of the affected color field.

How can I determine whether content may already be malicious?

Review stored color-field values for entries that begin with rgb() or hsl() but contain additional trailing HTML or other unexpected content. Such values may have bypassed validation and execute when rendered.

What is the remediation?

Upgrade ApostropheCMS to version 4.34.0, which fixes the validation issue. If an upgrade is not immediately possible, restrict edit access to trusted users and inspect stored color-field values for trailing content.

CVE-2026-112951: ApostropheCMS: Color field validation bypass allows stored XSS via HTML appended after rgb()/hsl() prefix

Affected Software

Remediation

Event History

Frequently Asked Questions

Who can exploit this issue?

Are default color-field deployments affected?

How can I determine whether content may already be malicious?

What is the remediation?

Company

Resources

Contact

Frequently Asked Questions

Who can exploit this issue?

Are default color-field deployments affected?

How can I determine whether content may already be malicious?

What is the remediation?