CVE-2026-33889 (GCVE-0-2026-33889)
Vulnerability from cvelistv5 – Published: 2026-04-15 19:29 – Updated: 2026-04-15 19:29
VLAI?
Title
ApostropheCMS: Stored XSS via CSS Custom Property Injection in `@apostrophecms/color-field` Escaping Style Tag Context
Summary
ApostropheCMS is an open-source Node.js content management system. Versions 4.28.0 and prior contain a stored cross-site scripting vulnerability in the @apostrophecms/color-field module, where color values prefixed with -- bypass TinyColor validation intended for CSS custom properties, and the launder.string() call performs only type coercion without stripping HTML metacharacters. These unsanitized values are then concatenated directly into <style> tags both in per-widget style elements rendered for all visitors and in the global stylesheet rendered for editors, with the output marked as safe HTML. An editor can inject a value which closes the style tag and executes arbitrary JavaScript in the browser of every visitor to any page containing the affected widget. This enables mass session hijacking, cookie theft, and privilege escalation to administrative control if an admin views draft content. This issue has been fixed in version 4.29.0.
Severity ?
5.4 (Medium)
CWE
- CWE-79 - Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Assigner
References
| URL | Tags | |||||||
|---|---|---|---|---|---|---|---|---|
|
||||||||
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| apostrophecms | apostrophe |
Affected:
< 4.29.0
|
{
"containers": {
"cna": {
"affected": [
{
"product": "apostrophe",
"vendor": "apostrophecms",
"versions": [
{
"status": "affected",
"version": "\u003c 4.29.0"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "ApostropheCMS is an open-source Node.js content management system. Versions 4.28.0 and prior contain a stored cross-site scripting vulnerability in the @apostrophecms/color-field module, where color values prefixed with -- bypass TinyColor validation intended for CSS custom properties, and the launder.string() call performs only type coercion without stripping HTML metacharacters. These unsanitized values are then concatenated directly into \u003cstyle\u003e tags both in per-widget style elements rendered for all visitors and in the global stylesheet rendered for editors, with the output marked as safe HTML. An editor can inject a value which closes the style tag and executes arbitrary JavaScript in the browser of every visitor to any page containing the affected widget. This enables mass session hijacking, cookie theft, and privilege escalation to administrative control if an admin views draft content. This issue has been fixed in version 4.29.0."
}
],
"metrics": [
{
"cvssV3_1": {
"attackComplexity": "LOW",
"attackVector": "NETWORK",
"availabilityImpact": "NONE",
"baseScore": 5.4,
"baseSeverity": "MEDIUM",
"confidentialityImpact": "LOW",
"integrityImpact": "LOW",
"privilegesRequired": "LOW",
"scope": "CHANGED",
"userInteraction": "REQUIRED",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N",
"version": "3.1"
}
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-79",
"description": "CWE-79: Improper Neutralization of Input During Web Page Generation (\u0027Cross-site Scripting\u0027)",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-04-15T19:29:50.899Z",
"orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
"shortName": "GitHub_M"
},
"references": [
{
"name": "https://github.com/apostrophecms/apostrophe/security/advisories/GHSA-97v6-998m-fp4g",
"tags": [
"x_refsource_CONFIRM"
],
"url": "https://github.com/apostrophecms/apostrophe/security/advisories/GHSA-97v6-998m-fp4g"
},
{
"name": "https://github.com/apostrophecms/apostrophe/commit/6a89bdb7acdb2e1e9bf1429961a6ba7f99410481",
"tags": [
"x_refsource_MISC"
],
"url": "https://github.com/apostrophecms/apostrophe/commit/6a89bdb7acdb2e1e9bf1429961a6ba7f99410481"
}
],
"source": {
"advisory": "GHSA-97v6-998m-fp4g",
"discovery": "UNKNOWN"
},
"title": "ApostropheCMS: Stored XSS via CSS Custom Property Injection in `@apostrophecms/color-field` Escaping Style Tag Context"
}
},
"cveMetadata": {
"assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
"assignerShortName": "GitHub_M",
"cveId": "CVE-2026-33889",
"datePublished": "2026-04-15T19:29:50.899Z",
"dateReserved": "2026-03-24T15:10:05.682Z",
"dateUpdated": "2026-04-15T19:29:50.899Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"vulnerability-lookup:meta": {
"nvd": "{\"cve\":{\"id\":\"CVE-2026-33889\",\"sourceIdentifier\":\"security-advisories@github.com\",\"published\":\"2026-04-15T20:16:35.850\",\"lastModified\":\"2026-04-15T20:16:35.850\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"ApostropheCMS is an open-source Node.js content management system. Versions 4.28.0 and prior contain a stored cross-site scripting vulnerability in the @apostrophecms/color-field module, where color values prefixed with -- bypass TinyColor validation intended for CSS custom properties, and the launder.string() call performs only type coercion without stripping HTML metacharacters. These unsanitized values are then concatenated directly into \u003cstyle\u003e tags both in per-widget style elements rendered for all visitors and in the global stylesheet rendered for editors, with the output marked as safe HTML. An editor can inject a value which closes the style tag and executes arbitrary JavaScript in the browser of every visitor to any page containing the affected widget. This enables mass session hijacking, cookie theft, and privilege escalation to administrative control if an admin views draft content. This issue has been fixed in version 4.29.0.\"}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"security-advisories@github.com\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N\",\"baseScore\":5.4,\"baseSeverity\":\"MEDIUM\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"LOW\",\"userInteraction\":\"REQUIRED\",\"scope\":\"CHANGED\",\"confidentialityImpact\":\"LOW\",\"integrityImpact\":\"LOW\",\"availabilityImpact\":\"NONE\"},\"exploitabilityScore\":2.3,\"impactScore\":2.7}]},\"weaknesses\":[{\"source\":\"security-advisories@github.com\",\"type\":\"Primary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-79\"}]}],\"references\":[{\"url\":\"https://github.com/apostrophecms/apostrophe/commit/6a89bdb7acdb2e1e9bf1429961a6ba7f99410481\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/apostrophecms/apostrophe/security/advisories/GHSA-97v6-998m-fp4g\",\"source\":\"security-advisories@github.com\"}]}}"
}
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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