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CVE-2026-41305— PostCSS has XSS via Unescaped </style> in its CSS Stringify Output

Quick assessment

Affected
postcss postcss
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

PostCSS是PostCSS开源的一个样式转换工具。 PostCSS 8.5.10之前版本存在跨站脚本漏洞，该漏洞源于在字符串化CSS AST时未转义</style>序列，可能导致用户提交的CSS被解析并重新字符串化以嵌入HTML<style>标签时，CSS值中的</style>跳出样式环境，从而引发跨站脚本攻击。

CVSS 6.1 · Medium EPSS 0.26% · P16

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application
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I. Basic Information for CVE-2026-41305

Vulnerability Information
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Vulnerability Title
PostCSS has XSS via Unescaped </style> in its CSS Stringify Output
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
在Web页面生成时对输入的转义处理不恰当(跨站脚本)
Source: CVE Program / CVE List V5
Vulnerability Title
PostCSS 跨站脚本漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
PostCSS是PostCSS开源的一个样式转换工具。 PostCSS 8.5.10之前版本存在跨站脚本漏洞，该漏洞源于在字符串化CSS AST时未转义</style>序列，可能导致用户提交的CSS被解析并重新字符串化以嵌入HTML<style>标签时，CSS值中的</style>跳出样式环境，从而引发跨站脚本攻击。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
postcss postcss < 8.5.10 -

II. Public POCs for CVE-2026-41305

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III. Intelligence Information for CVE-2026-41305

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Vendor Advisories for CVE-2026-41305 (1)

IV. Related Vulnerabilities

Same product: postcss
Same vendor: postcss
Same weakness: CWE-79

V. Comments for CVE-2026-41305

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