# CVE-2026-125338: Winter CMS: Stored XSS through cached Brand Settings and Editor Settings custom styles


- **Severity:** Medium 4.5 (`CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:U/C:N/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 10 Nov 2026
- **Updated:** 10 Nov 2026
- **Also known as:** GHSA-5cwr-5jxg-pcf6

## What is CVE-2026-125338?

CVE-2026-125338 is a medium-severity vulnerability in wintercms winter, published on 10 Nov 2026. 

### Official description

Winter CMS is a content management system built on the Laravel PHP framework. Prior to 1.2.14, BrandSetting::renderCss() and EditorSetting::renderCss() store raw LESS compiler output with Cache::forever() but apply strip_tags() only to the value returned on a cache miss. The first render after saving custom CSS appears sanitized while priming an unsafe cache entry, and later cache hits return unsanitized output into the backend style element, allowing a user with backend.manage_branding or backend.manage_editor to cause stored cross-site scripting when another backend page renders the styles. The styles also appear on unauthenticated backend sign-in, password restore, and password reset layouts. This issue is fixed in version 1.2.14.

Weakness: CWE-79 (Improper Neutralization of Input During Web Page Generation)

## Which versions are affected by CVE-2026-125338?

1 open source package ship an affected version, including winter/wn-backend-module.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `winter/wn-backend-module` | Packagist | All versions | 1.2.14 |

## How do I fix CVE-2026-125338?

Upgrade winter/wn-backend-module to 1.2.14 or later.

## Is CVE-2026-125338 being exploited?

There is no known exploitation of CVE-2026-125338 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-125338 and fix it if it is affected.

What it is: CVE-2026-125338 is a medium-severity vulnerability in wintercms winter, published on 10 Nov 2026. 
Exploitation: There is no known exploitation of CVE-2026-125338 in the wild and no public exploit code.

Affected packages and fixed versions:
- winter/wn-backend-module (Packagist): affected all versions; fixed in 1.2.14

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-125338/ (Markdown: https://insights.sbomify.com/CVE-2026-125338/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-125338
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-125338
- OSV: https://osv.dev/vulnerability/CVE-2026-125338

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-125338/
Summaries are generated and may contain mistakes; the official description above is the record.