Umbraco is an ASP.NET content management system (CMS). Starting in 10.0.0 and prior to versions 10.8.1 and 12.3.4, Umbraco contains a cross-site scripting (XSS) vulnerability enabling attackers to bring malicious content into a website or application. Versions 10.8.1 and 12.3.4 contain a patch for this issue.