XWiki Platform is a generic wiki platform. Starting in version 9.7-rc-1 and prior to versions 15.10.11, 16.4.1, and 16.5.0, any user with an account can perform arbitrary remote code execution by adding instances of `XWiki.WikiMacroClass` to any page. This compromises the confidentiality, integrity and availability of the whole XWiki installation. This vulnerability has been fixed in XWiki 15.10.11, 16.4.1 and 16.5.0. It is possible to manually apply the patch to the page `XWiki.XWikiSyntaxMacrosList` as a workaround.