The API in Zabbix before 1.8.20rc1, 2.0.x before 2.0.11rc1, and 2.2.x before 2.2.2rc1 allows remote authenticated users to spoof arbitrary users via the user name in a user.login request.
https://support.zabbix.com/browse/ZBX-7703
http://www.securityfocus.com/bid/65402
http://lists.fedoraproject.org/pipermail/package-announce/2014-May/132377.html
http://lists.fedoraproject.org/pipermail/package-announce/2014-May/132376.html