CVE-2023-37269 is a low-severity (CVSS 2) Cross-site Scripting (XSS) vulnerability in wintercms/winter. 2 public exploit references exist, so weaponization risk is real. A fix is available for wintercms/winter — see the affected versions and patch details below.
Winter CMS vulnerable to stored XSS through privileged upload of SVG file
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.
How urgent is this, really
CVE-2023-37269 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,567 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
wintercms/winterReal-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 the backend.manage_branding 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 said, all users are advised to update to the latest version (1.2.3) to ensure their systems remain secure.
Patches
This issue has been patched in v1.2.3 through the inclusion of full support for SVG uploads and automatic sanitization of uploaded SVG files.
Workarounds
Apply https://github.com/wintercms/storm/commit/186d85d8fea2cae43afc807d39f68553c24e56be & https://github.com/wintercms/winter/commit/fa50b4c7489b67ea80072f8ac9fe5294fce1df1c manually if unable to upgrade to v1.2.3.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | wintercms/winter | all versions | 1.2.3composer require wintercms/winter:^1.2.3 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
WinterCMS < 1.2.3 - Persistent Cross-Site Scripting
by abhishek morla · Jul 15, 2023
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for wintercms/winter, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update wintercms/winter to 1.2.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-37269 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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2023-37269 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2023-37269. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2023-37269 in your dependencies?
O3 Security finds CVE-2023-37269 across Packagist dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.