XWiki Platform is a generic wiki platform. Prior to 15.10.14, 16.4.6, and 16.10.0-rc-1, its possible for an user to get access to private information through the REST API - but could also be through another API - when a sub wiki is using Prevent unregistered users to view pages. The vulnerability only affects subwikis, and it only concerns specific right options such as Prevent unregistered users to view pages. or Prevent unregistered users to edit pages. Its possible to detect the vulnerability by enabling Prevent unregistered users to view pages and then trying to access a page through the REST API without using any credentials. The vulnerability has been patched in XWiki 15.10.14, 16.4.6 and 16.10.0RC1.
The product does not properly assign, modify, track, or check privileges for an actor, creating an unintended sphere of control for that actor.