You signed in with another tab or window. Reload to refresh your session.You signed out in another tab or window. Reload to refresh your session.You switched accounts on another tab or window. Reload to refresh your session.Dismiss alert
PostCSS: XSS via Unescaped </style> in CSS Stringify Output
Summary
PostCSS v8.5.5 (latest) does 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.
Proof of Concept
constpostcss=require('postcss');// Parse user CSS and re-stringify for page embeddingconstuserCSS='body { content: "</style><script>alert(1)</script><style>"; }';constast=postcss.parse(userCSS);constoutput=ast.toResult().css;consthtml=`<style>${output}</style>`;console.log(html);// <style>body { content: "</style><script>alert(1)</script><style>"; }</style>//// Browser: </style> closes the style tag, <script> executes
Tested output (Node.js v22, postcss v8.5.5):
Input: body { content: "</style><script>alert(1)</script><style>"; }
Output: body { content: "</style><script>alert(1)</script><style>"; }
Contains </style>: true
Impact
Impact non-bundler use cases since bundlers for XSS on their own. Requires some PostCSS plugin to have malware code, which can inject XSS to website.
Renovate failed to update an artifact related to this branch. You probably do not want to merge this PR as-is.
♻ Renovate will retry this branch, including artifacts, only when one of the following happens:
any of the package files in this branch needs updating, or
the branch becomes conflicted, or
you click the rebase/retry checkbox if found above, or
you rename this PR's title to start with "rebase!" to trigger it manually
The artifact failure details are included below:
File name: pnpm-lock.yaml
Scope: all 97 workspace projects
Progress: resolved 1, reused 0, downloaded 0, added 0
examples/ui-prompting-examples | WARN deprecated @types/uuid@11.0.0
Progress: resolved 39, reused 0, downloaded 0, added 0
Progress: resolved 61, reused 0, downloaded 0, added 0
Progress: resolved 114, reused 0, downloaded 0, added 0
/tmp/renovate/repos/github/SAP/open-ux-tools/packages/backend-proxy-middleware-cf:
ERR_PNPM_UNSUPPORTED_ENGINE Unsupported environment (bad pnpm and/or Node.js version)
This error happened while installing a direct dependency of /tmp/renovate/repos/github/SAP/open-ux-tools/packages/backend-proxy-middleware-cf
Your Node version is incompatible with "@sap/approuter@20.10.0".
Expected version: ^20.0.0 || ^22.0.0
Got: v24.15.0
This is happening because the package's manifest has an engines.node field specified.
To fix this issue, install the required Node version.
Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.
This PR includes no changesets
When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types
renovateBot
changed the title
fix(deps): update dependency postcss to v8.5.10 [security]
fix(deps): update dependency postcss to v8.5.10 [security] - autoclosed
May 6, 2026
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
This PR contains the following updates:
8.5.8→8.5.10PostCSS has XSS via Unescaped </style> in its CSS Stringify Output
CVE-2026-41305 / GHSA-qx2v-qp2m-jg93
More information
Details
PostCSS: XSS via Unescaped
</style>in CSS Stringify OutputSummary
PostCSS v8.5.5 (latest) does 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.Proof of Concept
Tested output (Node.js v22, postcss v8.5.5):
Impact
Impact non-bundler use cases since bundlers for XSS on their own. Requires some PostCSS plugin to have malware code, which can inject XSS to website.
Suggested Fix
Escape
</stylein all stringified output values:Credits
Discovered and reported by Sunil Kumar (@TharVid)
Severity
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:NReferences
This data is provided by the GitHub Advisory Database (CC-BY 4.0).
Release Notes
postcss/postcss (postcss)
v8.5.10Compare Source
</style>in non-bundler cases (by @TharVid).v8.5.9Compare Source
Configuration
📅 Schedule: (in timezone America/Los_Angeles)
🚦 Automerge: Disabled by config. Please merge this manually once you are satisfied.
♻ Rebasing: Whenever PR is behind base branch, or you tick the rebase/retry checkbox.
🔕 Ignore: Close this PR and you won't be reminded about this update again.
This PR was generated by Mend Renovate. View the repository job log.