💣 Privilege escalation (PR) through realtime WYSIWYG editing in XWiki (xwiki xwiki-platform)

Description

XWiki Platform is a generic wiki platform offering runtime services for applications built on top of it. NOTE: The Realtime WYSIWYG Editor extension was **experimental**, and thus **not recommended**, in the versions affected by this vulnerability. It has become enabled by default, and thus recommended, starting with XWiki 16.9.0. A user with only **edit right** can join a realtime editing session where others, that where already there or that may join later, have **script** or **programming** access rights. This user can then insert **script rendering macros** that are executed for those users in the realtime session that have script or programming rights. The inserted scripts can be used to gain more access rights. This vulnerability has been patched in XWiki 15.10.2, 16.4.1 and 16.6.0-rc-1. Users are advised to upgrade. Users unable to upgrade may either disable the realtime WYSIWYG editing by disabling the ``xwiki-realtime`` CKEditor plugin from the WYSIWYG editor administration section or uninstall the Realtime WYSIWYG Editorextension (org.xwiki.platform:xwiki-platform-realtime-wysiwyg-ui).