Winter: Stored XSS through cached Brand Settings and Editor Settings custom styles

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

4.5 · CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:U/C:N/I:H/A:N

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

Impact Users with the backend.managebranding ("Customize the back-end") or backend.manageeditor ("Manage global code editor preferences") permission can provide custom CSS through Settings → Customize Backend → Styles or Settings → Editor Settings → Markup Styles that is compiled through the LESS CSS parser and rendered on every backend page. v1.2.13 addressed CVE-2026-32257 and CVE-2026-32258 by applying striptags() to the compiled output of BrandSetting::renderCss() and EditorSetting::renderCss(). That fix was incomplete. Both methods cache the raw compiler output with Cache::forever() and applied striptags() only to the value returned on a cache miss, so every subsequent cache hit returned the unsanitized value directly into the backend <style element. The first page render after saving therefore appears sanitized while priming an unsafe cache entry, and the stored XSS remains exploitable from the second render onwards. Because the custom styles partial is included by both the…

Published by the source

20 Aug 2026, 18:44 UTC

Last modified by the source

20 Aug 2026, 19:00 UTC

Source last checked

26 Oct 2026, 14:50 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-5cwr-5jxg-pcf6

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-5cwr-5jxg-pcf6

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# Patch Next advisory brief: GHSA-5cwr-5jxg-pcf6

Advisory: Winter: Stored XSS through cached Brand Settings and Editor Settings custom styles
IDs: GHSA-5cwr-5jxg-pcf6
Record: https://patchnext.com/advisories/ghsa-5cwr-5jxg-pcf6 (revision 2, source checked 26 Oct 2026, 14:50 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 4.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: winter/wn-backend-module 1.2.14. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist winter/wn-backend-module: affected <= 1.2.13; fixed in 1.2.14

## Suggested inspection (read-only)
- Packagist winter/wn-backend-module: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on winter/wn-backend-module.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-5cwr-5jxg-pcf6 (OSV record GHSA-5cwr-5jxg-pcf6 lists affected ranges: Packagist winter/wn-backend-module >=0 <1.2.14 (fixed))
- Verified: https://github.com/advisories/GHSA-5cwr-5jxg-pcf6 (GitHub-reviewed advisory GHSA-5cwr-5jxg-pcf6 lists affected ranges: Packagist winter/wn-backend-module >=0 <=1.2.13)

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