{"id":"GHSA-vrqc-59mw-qqg7","summary":"Umbraco has Stored XSS in UFM Rendering Pipeline via Permissive DOMPurify Attribute Filtering","details":"### Description\nAn 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.\n\n### Impact\nAs 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.\n\n### Patches\nThe issue is patched in 16.5.1 and 17.2.2.\n\n### Workarounds\nThere is no workaround other than upgrading.\n\n### References\nhttps://docs.umbraco.com/umbraco-cms/reference/umbraco-flavored-markdown","aliases":["CVE-2026-31833"],"modified":"2026-03-13T08:11:23.767315Z","published":"2026-03-11T14:54:00Z","database_specific":{"github_reviewed":true,"github_reviewed_at":"2026-03-11T14:54:00Z","nvd_published_at":"2026-03-10T22:16:21Z","cwe_ids":["CWE-79"],"severity":"MODERATE"},"references":[{"type":"WEB","url":"https://github.com/umbraco/Umbraco-CMS/security/advisories/GHSA-vrqc-59mw-qqg7"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-31833"},{"type":"PACKAGE","url":"https://github.com/umbraco/Umbraco-CMS"}],"affected":[{"package":{"name":"Umbraco.Cms","ecosystem":"NuGet","purl":"pkg:nuget/Umbraco.Cms"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"16.2.0"},{"fixed":"16.5.1"}]}],"versions":["16.2.0","16.3.0","16.3.0-rc","16.3.0-rc2","16.3.0-rc3","16.3.0-rc4","16.3.1","16.3.2","16.3.3","16.3.4","16.4.0","16.4.0-rc","16.4.0-rc2","16.4.1","16.5.0","16.5.0-rc"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/03/GHSA-vrqc-59mw-qqg7/GHSA-vrqc-59mw-qqg7.json"}},{"package":{"name":"Umbraco.Cms","ecosystem":"NuGet","purl":"pkg:nuget/Umbraco.Cms"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"17.0.0"},{"fixed":"17.2.2"}]}],"versions":["17.0.0","17.0.1","17.0.2","17.1.0","17.1.0-rc","17.2.0","17.2.0-rc","17.2.0-rc2","17.2.1"],"database_specific":{"last_known_affected_version_range":"\u003c 17.2.1","source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/03/GHSA-vrqc-59mw-qqg7/GHSA-vrqc-59mw-qqg7.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:L"}]}