XWiki Rendering is a generic rendering system that converts textual input in a given syntax (wiki syntax, HTML, etc) into another syntax (XHTML, etc). Starting in version 5.4.5 and prior to version 14.10, the XHTML syntax depended on the "xdom+xml/current" syntax which allows the creation of raw blocks that permit the insertion of arbitrary HTML content including JavaScript. This allows XSS attacks for users who can edit a document like their user profile (enabled by default). This has been fixed in version 14.10 by removing the dependency on the "xdom+xml/current" syntax from the XHTML syntax. Note that the "xdom+xml" syntax is still vulnerable to this attack. As it's main purpose is testing and its use is quite difficult, this syntax shouldn't be installed or used on a regular wiki. There are no known workarounds apart from upgrading.