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.NET
.NET NuGet
Not in CISA KEV
MEDIUM severity

CVE-2025-56236 — FormCMS

MEDIUM

CVE-2025-56236 is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) vulnerability in FormCMS. A fix is available for FormCMS — see the affected versions and patch details below.

FormCms avatar upload feature has a stored cross-site scripting (XSS) vulnerability

Also known asGHSA-4fxf-xgrm-8fcj
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Nov 2, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2025-56236.

EPSS Exploitation Probability

via FIRST.org ↗
0.2%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs10th percentile — riskier than 10% of all scored CVEsHighest risk
0.00%0.24%0.47%0.71%0.0%0.2%May 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected
.NETFormCMS

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects NuGet packages — download data is not available via public APIs for these ecosystems.

Description

FormCms v0.5.5 contains a stored cross-site scripting (XSS) vulnerability in the avatar upload feature. Authenticated users can upload .html files containing malicious JavaScript, which are accessible via a public URL. When a privileged user accesses the file, the script executes in their browser context.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
.NETNuGetFormCMSall versions0.5.7dotnet add package FormCMS --version 0.5.7

Affected Products

1 product · 1 configurations
Application
formcmsformcms
≥ 0.5.5 && < 0.5.7
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for FormCMS, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update FormCMS to 0.5.7 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-56236 is resolved across your whole dependency graph.

  3. Workarounds

    Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Frequently Asked Questions

FormCms v0.5.5 contains a stored cross-site scripting (XSS) vulnerability in the avatar upload feature. Authenticated users can upload .html files containing malicious JavaScript, which are accessible via a public URL. When a privileged user accesses the file, the script executes in their browser context.
O3 Security · Impact-Aware SCA

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CVE-2025-56236: FormCMS XSS — Fixed in 0.5.7