The mysql user parameter configuration script (userparameter_mysql.conf) in the agent in Zabbix before 2.0.18, 2.2.x before 2.2.13, and 3.0.x before 3.0.3, when used with a shell other than bash, allows context-dependent attackers to execute arbitrary code or SQL commands via the mysql.size parameter.
https://www.zabbix.com/documentation/3.0/manual/introduction/whatsnew303#miscellaneous_improvements
https://www.zabbix.com/documentation/2.2/manual/introduction/whatsnew2213#miscellaneous_improvements
https://www.zabbix.com/documentation/2.0/manual/introduction/whatsnew2018#miscellaneous_improvements
https://security.gentoo.org/glsa/201612-42
http://www.securityfocus.com/bid/89631
http://www.securityfocus.com/archive/1/538258/100/0/threaded