XWiki Platform is a generic wiki platform offering runtime services for applications built on top of it. By either creating a new or editing an existing document with an icon set, an attacker can inject XWiki syntax and Velocity code that is executed with programming rights and thus allows remote code execution. There are different attack vectors, the simplest is the Velocity code in the icon set's HTML or XWiki syntax definition. The [icon picker](https://extensions.xwiki.org/xwiki/bin/view/Extension/Icon%20Theme%20Application#HIconPicker) can be used to trigger the rendering of any icon set. The XWiki syntax variant of the icon set is also used without any escaping in some documents, allowing to inject XWiki syntax including script macros into a document that might have programming right, for this the currently used icon theme needs to be edited. Further, the HTML output of the icon set is output as JSON in the icon picker and this JSON is interpreted as XWiki syntax, allowing again…