XWiki Platform is a generic wiki platform. Starting in version 3.3-milestone-2 and prior to versions 14.10.4 and 15.0-rc-1, it's possible for a user to execute anything with the right of the author of the XWiki.ClassSheet document. This has been patched in XWiki 15.0-rc-1 and 14.10.4. There are no known workarounds.