XWiki Platform is a generic wiki platform. Starting in version 3.3-milestone-1 and prior to versions 15.10.9 and 16.3.0, on instances where Extension Repository Application
is installed, any user can execute any code requiring programming
rights on the server. This vulnerability has been fixed in XWiki 15.10.9 and 16.3.0. Since Extension Repository Application
is not mandatory, it can be safely disabled on instances that do not use it as a workaround. It is also possible to manually apply the patches from commit 8659f17d500522bf33595e402391592a35a162e8 to the page ExtensionCode.ExtensionSheet
and to the page ExtensionCode.ExtensionAuthorsDisplayer
.