fkie_cve-2026-112951

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.

GHSA-vmgj-9cwm-cf3h — ApostropheCMS: Color field validation bypass allows stored XSS via HTML appended after rgb()/hsl() prefix

Affected: npm: apostrophe

### 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

| 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 bo…

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fkie_cve-2026-112951

GHSA-vmgj-9cwm-cf3h — ApostropheCMS: Color field validation bypass allows stored XSS via HTML appended after rgb()/hsl() prefix