GHSA-vrqc-59mw-qqg7
Umbraco has Stored XSS in UFM Rendering Pipeline via Permissive DOMPurify Attribute Filtering
Packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| NuGet | Umbraco.Cms | >= 16.2.0, < 16.5.1 | 16.5.1 |
| NuGet | Umbraco.Cms | >= 17.0.0, < 17.2.2 | 17.2.2 |
Details
As written in the advisory (Markdown source, shown as plain text).
### Description
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.
### Impact
As property type descriptions support Markdown/HTML via the UFM rendering pipeline, injected event handlers are rendered in the backoffice interface, resulting in a stored XSS affecting other backoffice users.
### Patches
The issue is patched in 16.5.1 and 17.2.2.
### Workarounds
There is no workaround other than upgrading.
### References
https://docs.umbraco.com/umbraco-cms/reference/umbraco-flavored-markdown
References
External links from the advisory. They lead to third-party sites.