{"id":"CVE-2020-5809","aliases":["GHSA-95qr-67rx-9pgh"],"url":"https://o3.security/vulnerability/CVE-2020-5809","summary":"Umbraco CMS vulnerable to stored XSS","details":"A stored XSS vulnerability exists in Umbraco CMS <= 8.9.1 or current. An authenticated user can inject arbitrary JavaScript code into iframes when editing content using the TinyMCE rich-text editor, as TinyMCE is configured to allow iframes by default in Umbraco CMS.","published":"2020-12-30T16:15:12.320Z","modified":"2026-07-08T19:45:23.883058Z","cvss":{"score":5.4,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N"},"epss":null,"cisaKev":null,"exploitsKnown":1,"affectedPackages":[{"ecosystem":"NuGet","name":"UmbracoCms.Core","fixedVersion":null}],"fix":null,"references":[{"type":"EVIDENCE","url":"https://www.tenable.com/security/research/tra-2020-59"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-07-08T19:45:23.883058Z"}}