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`.
XWiki Platform is a generic wiki platform. The REST API exposes the history of any page in XWiki of which the attacker knows the name. The exposed information includes for each modification of the page the time of the modification, the version number, the author of the modification (both username and displayed name) and the version comment. This information is exposed regardless of the rights setup, and even when the wiki is configured to be fully private. On a private wiki, this can be tested by accessing /xwiki/rest/wikis/xwiki/spaces/Main/pages/WebHome/history, if this shows the history of the main page then the installation is vulnerable. This has been patched in XWiki 15.10.9 and XWiki 16.3.0RC1.
XWiki Platform is a generic wiki platform offering runtime services for applications built on top of it. By creating a conflict when another user with more rights is currently editing a page, it is possible to execute JavaScript snippets on the side of the other user, which compromises the confidentiality, integrity and availability of the whole XWiki installation. This has been patched in XWiki 15.10.8 and 16.3.0RC1.