Privilege escalation (PR)/remote code execution from account through Menu.UIExtensionSheet

XWiki Platform is a generic wiki platform offering runtime services for applications built on top of it. Starting in version 5.1-rc-1 and prior to versions 14.10.8 and 15.3-rc-1, any user who can edit their own user profile can execute arbitrary script macros including Groovy and Python macros that allow remote code execution including unrestricted read and write access to all wiki contents. This has been patched in XWiki 14.10.8 and 15.3-rc-1 by adding proper escaping. As a workaround, the patch can be manually applied to the document `Menu.UIExtensionSheet`; only three lines need to be changed.