CVE-2026-41305CWE-79

PostCSS has XSS via Unescaped </style> in its CSS Stringify Output

Medium · published April 24, 2026

CVSS v3.1
6.1
EPSS
0%
Percentile
17.1
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
6.1 · MEDIUM
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
CVSS v4.0
Not supplied
EPSS
0.00263 · 17.1th percentile
Weakness
CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Published
2026-04-24T02:27Z
EPSS history
Timeline
  • 24 APR 02:27Z
    PostCSS has XSS via Unescaped </style> in its CSS Stringify Output
    cvelistv5