Summary
ApostropheCMS: Color field validation bypass allows stored XSS via HTML appended after rgb()/hsl() prefix
The color field accepts any string that begins with a valid rgb() / hsl() color, because TinyColor.isValid does not anchor its match at the end of the string. 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.
Details
Server-side validation of the color field relies on TinyColor:
const { TinyColor } = require('@ctrl/tinycolor');
if (!new TinyColor(value).isValid) throw self.apos.error('invalid');
TinyColor's rgb/hsl matchers are not anchored at the end of the string, while hex matchers are. Tested with @ctrl/tinycolor
| Input | isValid |
|---|---|
rgb(1,2,3)<img src=x onerror=alert(1)> |
true |
rgb(1,2,3)</textarea><script>alert(1)</script> |
true |
hsl(0,100%,50%);--x:1}</style><script>alert(1)</script> |
true |
#ff0000<img src=x onerror=alert(1)> |
false |
The value is saved to MongoDB unchanged (not normalized to hex8).
Relation to GHSA-97v6-998m-fp4g
GHSA-97v6 addressed CSS custom property injection escaping a <style> context. The root cause (validation that accepts trailing content after a valid color) still exists in <= 4.32.2, so [FILL IN: either "the style-tag sink remains exploitable via </style>" OR "a separate HTML sink at X is exploitable"]. Fixing the validation (requiring the full string to be a color, or storing only TinyColor's normalized output) would close both.
Impact
Any user with edit permission can plant persistent JavaScript that runs in the browser of visitors and administrators viewing the affected page, enabling session hijacking and actions as an admin.
Untrusted input is rendered as active markup in a victim's browser, which can run script in their session. Typical impact: session or credential theft, and actions taken as the user.
CVE-2026-112951 has a CVSS score of 5.4 (Medium). The vector is network-reachable, low privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (4.34.0); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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See it in your environmentNew to Kodem? Get a demo →Remediation advice
Reject values unless the entire string is a valid color, e.g. normalize on save:
const c = new TinyColor(value);
if (!c.isValid) throw self.apos.error('invalid');
value = c.toHex8String(); // store only normalized output
Frequently Asked Questions
- What is CVE-2026-112951? CVE-2026-112951 is a medium-severity cross-site scripting (XSS) vulnerability in apostrophe (npm), affecting versions < 4.34.0. It is fixed in 4.34.0. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
- How severe is CVE-2026-112951? CVE-2026-112951 has a CVSS score of 5.4 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of apostrophe are affected by CVE-2026-112951? apostrophe (npm) versions < 4.34.0 is affected.
- Is there a fix for CVE-2026-112951? Yes. CVE-2026-112951 is fixed in 4.34.0. Upgrade to this version or later.
- Is CVE-2026-112951 exploitable, and should I be worried? Whether CVE-2026-112951 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-112951 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-112951? Upgrade
apostropheto 4.34.0 or later.