XWiki is a generic wiki platform. In versions starting from 1.8.1 to before 14.10.22, from 15.0-rc-1 to before 15.10.12, from 16.0.0-rc-1 to before 16.4.3, and from 16.5.0-rc-1 to before 16.7.0, anyone can access the metadata of any attachment in the wiki using the wiki attachment REST endpoint. There is no filtering for the results depending on current user rights, meaning an unauthenticated user could exploit this even in a private wiki. This issue has been patched in versions 14.10.22, 15.10.12, 16.4.3, and 16.7.0.
The product does not perform an authorization check when an actor attempts to access a resource or perform an action.