Data leak of notification filters of users in XWiki Platform

Vulnerability Description

XWiki Platform is a generic wiki platform offering runtime services for applications built on top of it. It's possible to get access to notification filters of any user by using a URL such as `<hostname>xwiki/bin/get/XWiki/Notifications/Code/NotificationFilterPreferenceLivetableResults?outputSyntax=plain&type=custom&user=<username>`. This vulnerability impacts all versions of XWiki since 13.2-rc-1. The filters do not provide much information (they mainly contain references which are public data in XWiki), though some info could be used in combination with other vulnerabilities. This vulnerability has been patched in XWiki 14.10.21, 15.5.5, 15.10.1, 16.0RC1. The patch consists in checking the rights of the user when sending the data. Users are advised to upgrade. It's possible to workaround the vulnerability by applying manually the patch: it's possible for an administrator to edit directly the document `XWiki.Notifications.Code.NotificationFilterPreferenceLivetableResults` to apply the same changes as in the patch. See commit c8c6545f9bde6f5aade994aa5b5903a67b5c2582.

References

• https://github.com/xwiki/xwiki-platform/security/advisories/GHSA-pg4m-3gp6-hw4w
• https://github.com/xwiki/xwiki-platform/commit/c8c6545f9bde6f5aade994aa5b5903a67b5c2582
• https://jira.xwiki.org/browse/XWIKI-20336