CVE-2020-36238
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.
Source: CVE-2020-36238