PostCSS takes a CSS file and provides an API to analyze and modify its rules by transforming the rules into an Abstract Syntax Tree. Versions prior to 8.5.10 do not escape `</style>` sequences when stringifying CSS ASTs. When user-submitted CSS is parsed and re-stringified for embedding in HTML `<style>` tags, `</style>` in CSS values breaks out of the style context, enabling XSS. Version 8.5.10 fixes the issue.

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History

Fri, 24 Apr 2026 02:45:00 +0000

Type Values Removed Values Added
Description PostCSS takes a CSS file and provides an API to analyze and modify its rules by transforming the rules into an Abstract Syntax Tree. Versions prior to 8.5.10 do not escape `</style>` sequences when stringifying CSS ASTs. When user-submitted CSS is parsed and re-stringified for embedding in HTML `<style>` tags, `</style>` in CSS values breaks out of the style context, enabling XSS. Version 8.5.10 fixes the issue.
Title PostCSS has XSS via Unescaped </style> in its CSS Stringify Output
Weaknesses CWE-79
References
Metrics cvssV3_1

{'score': 6.1, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N'}


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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-04-24T02:27:47.719Z

Reserved: 2026-04-20T14:01:46.670Z

Link: CVE-2026-41305

cve-icon Vulnrichment

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cve-icon NVD

Status : Received

Published: 2026-04-24T03:16:11.547

Modified: 2026-04-24T03:16:11.547

Link: CVE-2026-41305

cve-icon Redhat

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cve-icon OpenCVE Enrichment

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Weaknesses