zKup CMS 2.0 through 2.3 does not require administrative authentication for admin/configuration/modifier.php, which allows remote attackers to gain administrator privileges via a direct request, as demonstrated by adding a new administrator.
https://www.exploit-db.com/exploits/5220
https://www.exploit-db.com/exploits/5219
https://exchange.xforce.ibmcloud.com/vulnerabilities/41068
http://www.zkup.fr/actualite-zkup/maj-critique-v203v204.html