Unrestricted file upload vulnerability in index.php in phpGreetCards 3.7 allows remote attackers to execute arbitrary PHP code by uploading a file with an executable extension, then accessing it via a via a link that is listed by userfiles/number_shell.php.
https://www.exploit-db.com/exploits/7561
https://exchange.xforce.ibmcloud.com/vulnerabilities/47591
http://www.vupen.com/english/advisories/2008/3510