GHSA-43w4-4j3c-jx29
LOWWinter CMS Stored XSS through Backend ColorPicker FormWidget
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Blast Radius
winter/wn-backend-moduleReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.
Description
Impact
Users with access to backend forms that include a ColorPicker FormWidget can provide a value that would then be rendered unescaped in the backend form, potentially allowing for a stored XSS attack.
By default, only the Brand Settings (backend.manage_branding) and Mail Brand Settings (system.manage_mail_templates) forms include the colorpicker formwidget, however it is also common for theme's to include it on their Theme Customization (cms.manage_theme_options) form.
Although this was a security issue, it's important to note that its severity is relatively low. To exploit the vulnerability, an attacker would already need to have trusted access to the Winter CMS backend and they would then need to convince a user with higher privileges than them to visit an affected Form in the backend.
These two factors limit the potential harm of this vulnerability. That being said, all users are advised to update to the latest version (1.2.4) to ensure their systems remain secure.
Patches
This issue has been patched in v1.2.4.
Workarounds
Apply https://github.com/wintercms/winter/commit/517f65dfae679b57575b047de13c5af48915a5ba manually if unable to upgrade to v1.2.4.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | winter/wn-backend-module | all versions | 1.2.4 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for winter/wn-backend-module. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update winter/wn-backend-module to 1.2.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-43w4-4j3c-jx29 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-43w4-4j3c-jx29 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-43w4-4j3c-jx29. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-43w4-4j3c-jx29 in your dependencies?
O3 detects GHSA-43w4-4j3c-jx29 across Packagist dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.