The remote web server hosts an application that is vulnerable to an information disclosure attack vector.
The version of JIRA installed on the remote host is earlier than 7.0.2 and is affected by a flaw related to the 'secure/ViewUserHover' script returning different error messages when validating the 'username' parameter. By using these different error messages, a remote attacker can enumerate valid usernames. While this information is often low risk, it is useful in carrying out additional, more focused attacks.
Update to JIRA 7.0.x version 7.0.2 or later.