Machine-written summary
Summary written by Claude Haiku from the source advisory. Not reviewed by a person.
Umbraco.Cms (NuGet) versions from 16.2.0 before 16.5.1 and from 17.0.0 before 17.2.2 are affected. An authenticated backoffice user with access to Settings can inject event handler attributes such as onclick and onload into property type descriptions, which are rendered by the UFM pipeline, enabling stored cross-site scripting against other backoffice users. Upgrade to 16.5.1 or 17.2.2. No workaround other than upgrading is given.
Not analysed yet
We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.
Severity and exploitation
| Score | Rating | CVSS | Vector | Source |
|---|---|---|---|---|
| 6.7 | Medium | 3.1 | CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:L | CNA (GitHub_M) |
- CISA KEV Not listed.
- EPSS 0.0030, the 23rd percentile, on 10 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.
Timeline
- 10 Mar 2026, 05:31 UTC Published by the maintainers as a GitHub repository advisory
- 31 Oct 2026, 15:22 UTC First seen by agentprime
- 31 Oct 2026, 15:22 UTC Confirmed by OSV