The /rest/api/1.0/render resource in Jira Server and Data Center before version 8.5.13, from version 8.6.0 before version 8.13.5, and from version 8.14.0 before version 8.15.1 allows remote anonymous attackers to determine if a username is valid or not via a missing permissions check.
The membersOf JQL search function in Jira Server and Data Center before version 8.5.13, from version 8.6.0 before version 8.13.5, and from version 8.14.0 before version 8.15.1 allows remote anonymous attackers to determine if a group exists & members of groups if they are assigned to publicly visible issue field.
Affected versions of Atlassian Jira Server and Data Center allow remote attackers to view the metadata of boards they should not have access to via an Insecure Direct Object References (IDOR) vulnerability. The affected versions are before version 8.5.10, and from version 8.6.0 before 8.13.2.