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

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

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.

Source published

20 Oct 2026 15:33:09 UTC

Source modified

20 Oct 2026 16:43:32 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: cve-program · CVE Program Terms of Use. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · 5.4 CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

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.

Source published

Oct 20, 2026, 3:33:09 PM (timezone not stated)

Source modified

Oct 20, 2026, 4:43:32 PM (timezone not stated)

Observed here

7 Nov 2026 04:33:46 UTC

Source terms

ENISA EUVD · source terms and attribution apply

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EUVD CVSS 3.1 · 5.4 CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

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.

Source published

20 Oct 2026 16:17:05 UTC

Source modified

20 Oct 2026 19:53:10 UTC

Observed here

25 Oct 2026 05:17:13 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · [email protected] · Secondary · 5.4 CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

### 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 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 ```

Source published

21 Oct 2026 17:05:44 UTC

Source modified

21 Oct 2026 17:15:08 UTC

Observed here

24 Oct 2026 13:17:17 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

Publisher rating · MODERATE