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.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| postcss | postcss | < 8.5.10 | — |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | node-postcss | 8.5.12+~cs9.3.32-1 | — |
| Debian 13 | node-postcss | No fix yet | — |
| Debian 12 | node-postcss | No fix yet | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 26.10 | node-postcss | No fix yet | — |
| Ubuntu 26.04 LTS | node-postcss | No fix yet | — |
| Ubuntu 25.10 | node-postcss | No fix yet | — |
| Ubuntu 24.04 LTS | node-postcss | No fix yet | — |
| Ubuntu 22.04 LTS | node-postcss | No fix yet | — |
Show 1 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 20.04 LTS | node-postcss | No fix yet | — |
Wolfi
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Wolfi rolling | jitsucom-jitsu-console | 2.11.0-r23 | — |
| Wolfi rolling | katib-earlystopping +8 | 0.19.0-r31 | — |
| Wolfi rolling | katib-suggestion-goptuna-compat | 0.19.0-r40 | — |
| Wolfi rolling | langfuse-3-worker | 3.164.0-r8 | — |
| Wolfi rolling | nextcloud-server-33 | 33.0.6-r6 | — |
| Wolfi rolling | renovate | 43.166.2-r0 | — |
| Wolfi rolling | saf | 1.6.0-r0 | — |
| Wolfi rolling | vite | 8.0.11-r0 | — |
| Wolfi rolling | vitess-23 | 23.0.4-r2 | — |
Affected packages
| Ecosystem | Package | Affected | Fixed | Record |
|---|---|---|---|---|
| npm | postcss | < 8.5.10 | 8.5.10 | GHSA-qx2v-qp2m-jg93 |
Advisories 2
- WID-SEC-2026-3046 IBM Concert: Mehrere Schwachstellen BSI CERT-Bund (WID) · Nov 10, 2026
- WID-SEC-2026-1654 IBM App Connect Enterprise: Mehrere Schwachstellen BSI CERT-Bund (WID) · Jun 28, 2026