CVE-2026-31833
Medium
Description
Umbraco is an ASP.NET CMS. From 16.2.0 to before 16.5.1 and 17.2.2, An authenticated backoffice user with access to Settings can inject malicious HTML into property type descriptions. Due to an overly permissive attributeNameCheck configuration (/.+/) in the UFM DOMPurify instance, event handler attributes such as onclick and onload, when used within Umbraco web components (umb-*, uui-*, ufm-*) were not filtered. This vulnerability is fixed in 16.5.1 and 17.2.2.
SeverityMedium
CVSS6.7
Exploit probability—
Product
Umbraco Cms
PublishedMar 10, 2026
First seenMar 10, 2026
Weakness typeCWE-79Cross-site scripting (XSS)
How to fix
Update
- umbraco umbraco_cms16.5.1, 17.2.2 or later
- Umbraco.Cms16.5.1, 17.2.2 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| umbraco umbraco_cms | 16.2.0 ≤ v < 16.5.1, 17.0.0 ≤ v < 17.2.2 | 16.5.1, 17.2.2 |
| Umbraco.CmsNuGet | 16.2.0 ≤ v < 16.5.1, 17.0.0 ≤ v < 17.2.2 | 16.5.1, 17.2.2 |
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