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Response snapshot Oct 27, 2026, 04:31 UTC

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VulnerabilityCVE-2026-112951

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

```js 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

At a glance

Exploited
Not known
Severity
5.4 Medium (CVSS 3.1)
Chance of exploitation
0.3% in the next 30 days
Sources
1 source

What to do

GitHub lists first patched versions: apostrophe: 4.34.0. Confirm the affected range and upgrade guidance in the exact advisory.

Read GitHub-reviewed advisory GHSA-vmgj-9cwm-cf3h (opens a new tab)

What happened

### Summary 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:

```js 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

Continue reading

| Input | `isValid` | |---|---| | `rgb(1,2,3) ` | `true` | | `rgb(1,2,3) ` | `true` | | `hsl(0,100%,50%);--x:1} ` | `true` | | `#ff0000 ` | `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 ``" 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.

### Suggested fix Reject values unless the entire string is a valid color, e.g. normalize on save: ```js const c = new TinyColor(value); if (!c.isValid) throw self.apos.error('invalid'); value = c.toHex8String(); // store only normalized output ```

Affected package ranges reported by GitHub: apostrophe: < 4.34.0

Scores and how they were measured

CVSS base severity

5.4

Version 3.1As of

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

Measurement source (opens a new tab)

How bad it is if exploited. Not a prediction of exploitation or proof you are exposed.

EPSS probability

0.3%

Scored Percentile 22.9%

Model and measurement source (opens a new tab)

A model's estimate of exploitation in the next 30 days, not certainty or your own risk.

Related technology

Sources

  1. Primary source

    GitHub-reviewed advisory GHSA-vmgj-9cwm-cf3h (opens a new tab)

    The public advisory supplies the description, affected package/version ranges, and any listed CVSS metric. GitHub review is not local review.

    Published Checked

  2. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-vmgj-9cwm-cf3h, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  3. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-vmgj-9cwm-cf3h, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  4. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-vmgj-9cwm-cf3h, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  5. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-vmgj-9cwm-cf3h, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  6. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-vmgj-9cwm-cf3h, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  7. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-vmgj-9cwm-cf3h, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  8. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-vmgj-9cwm-cf3h, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  9. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-vmgj-9cwm-cf3h, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  10. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-vmgj-9cwm-cf3h, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  11. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-vmgj-9cwm-cf3h, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  12. Primary source

    FIRST measured EPSS score (opens a new tab)

    Measured EPSS probability and percentile for CVE-2026-112951, scored 2026-10-26. This is a model estimate, not proof of exposure.

    Published Checked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, October 21). ApostropheCMS: Color field validation bypass allows stored XSS via HTML appended after rgb()/hsl() prefix (CVE-2026-112951). https://kevwire.com/record/CVE-2026-112951

MLA

"ApostropheCMS: Color field validation bypass allows stored XSS via HTML appended after rgb()/hsl() prefix (CVE-2026-112951)." KEVWire, 21 Oct. 2026, kevwire.com/record/CVE-2026-112951.

Chicago

KEVWire. "ApostropheCMS: Color field validation bypass allows stored XSS via HTML appended after rgb()/hsl() prefix (CVE-2026-112951)." Last modified October 21, 2026. https://kevwire.com/record/CVE-2026-112951.

Evidence summary (plain text)

ApostropheCMS: Color field validation bypass allows stored XSS via HTML appended after rgb()/hsl() prefix (Oct 21, 2026).
```js
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
CVSS 5.4 (version 3.1; evidence as of Oct 21, 2026; https://github.com/advisories/GHSA-vmgj-9cwm-cf3h).
EPSS 0.3% for the following 30 days, scored Oct 26, 2026 (https://api.first.org/data/v1/epss?cve=CVE-2026-112951&date=2026-10-26).
Sources:
GitHub-reviewed advisory GHSA-vmgj-9cwm-cf3h: https://github.com/advisories/GHSA-vmgj-9cwm-cf3h
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMlQxNTo1Mjo1NlrOAAfxiA%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMlQxNDowNjoxNFrOAAfxZw%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMlQwODoyNzoyM1rOAAYp9A%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMVQyMTozNTo1OFrOAAfwCQ%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMVQyMTozMDoxM1rOAAfv2A%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMVQyMToyODowOVrOAAfv1g%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMVQyMToyNDoyMFrOAAfv1Q%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMVQyMDo0NTowN1rOAAfvzQ%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMVQyMDozMDoyNlrOAAfvxw%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMVQyMDowMzo1N1rOAAfvxQ%3D%3D
FIRST measured EPSS score: https://api.first.org/data/v1/epss?cve=CVE-2026-112951&date=2026-10-26
Record ID: CVE-2026-112951.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Oct 27, 2026, 01:40 UTC. Ingestion is not an independent editorial investigation.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

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