XWiki is an open-source wiki software platform. When a user without script right creates a document with an XWiki.Notifications.Code.NotificationDisplayerClass object, and later an admin edits and saves that document, the possibly malicious content of that object is output as raw HTML, allowing XSS attacks. While the notification displayer executes Velocity, the existing generic analyzer already warns admins before editing Velocity code.

Note that warnings before editing documents with dangerous properties have only been introduced in XWiki 15.9, before that version, this was a known issue and the advice was simply to be careful. This vulnerability has been patched in XWiki 15.10.16, 16.4.7, and 16.10.2 by adding a required rights analyzer that warns the admin before editing about the possibly malicious code.