Winter CMS stored XSS through privileged upload of SVG file

Exploitation

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

CVSS

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

EPSS

• CVE-2023-37269: 2.70% estimated exploitation activity in the next 30 days; percentile 85.95 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact Users with the backend.managebranding permission can upload SVGs as the application logo. Previously, SVG uploads were not sanitized, which could have allowed a stored XSS attack. Although this was a security issue, it's important to note that its severity is low. To exploit the vulnerability, an attacker would already need to have developer or super user level permissions in Winter CMS. This means they would already have extensive access and control within the system. Additionally, to execute the XSS, the attacker would need to convince the victim to directly visit the URL of the maliciously uploaded SVG, and the application would have to be using local storage where uploaded files are served under the same domain as the application itself instead of a CDN. This is because all SVGs in Winter CMS are rendered through an img tag, which prevents any payloads from being executed directly. These two factors significantly limit the potential harm of this vulnerability. That being…

Published by the source

7 Jul 2023, 21:20 UTC

Last modified by the source

6 Nov 2023, 05:05 UTC

Source last checked

26 Oct 2026, 14:10 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-wjw2-4j7j-6gc3

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# Patch Next advisory brief: CVE-2023-37269

Advisory: Winter CMS stored XSS through privileged upload of SVG file
IDs: CVE-2023-37269, GHSA-wjw2-4j7j-6gc3
Record: https://patchnext.com/advisories/cve-2023-37269 (revision 1, source checked 26 Oct 2026, 14:10 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Low (CVSS 2.0)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: wintercms/winter 1.2.3. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist wintercms/winter: affected < 1.2.3; fixed in 1.2.3

## Suggested inspection (read-only)
- Packagist wintercms/winter: 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 wintercms/winter.
- 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://github.com/advisories/GHSA-wjw2-4j7j-6gc3 (GitHub-reviewed advisory GHSA-wjw2-4j7j-6gc3 lists affected ranges: Packagist wintercms/winter >=0 <1.2.3)

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