Incomplete blacklist vulnerability in NULL FTP Server Free and Pro 1.1.0.7 allows remote authenticated users to execute arbitrary commands via a custom SITE command containing shell metacharacters such as "&" (ampersand) in the middle of an argument.
https://www.exploit-db.com/exploits/7355
https://exchange.xforce.ibmcloud.com/vulnerabilities/47099
http://www.vwsolutions.com/knowledgeBase/releaseNotes.aspx?productId=14
http://www.vupen.com/english/advisories/2008/3367
http://www.securityfocus.com/bid/32656