The WikiManager REST API allows any user to create wikis

XWiki Platform is a generic wiki platform. Prior to 15.10.15, 16.4.6, and 16.10.0, any user can exploit the WikiManager REST API to create a new wiki, where the user could become an administrator and so performs other attacks on the farm. Note that this REST API is not bundled in XWiki Standard by default: it needs to be installed manually through the extension manager. The problem has been patched in versions 15.10.15, 16.4.6 and 16.10.0 of the REST module.