The UniversalAvatarResource.getAvatars resource in Jira Server and Data Center before version 8.9.0 allows remote attackers to obtain information about custom project avatars names via an Improper authorization vulnerability.
Versions before 8.9.1, Various resources in Jira responded with a 404 instead of redirecting unauthenticated users to the login page, in some situations this may have allowed unauthorised attackers to determine if certain resources exist or not through an Information Disclosure vulnerability.