The connection log file implementation in Grok Developments NetProxy 4.03 does not record requests that omit http:// in a URL, which might allow remote attackers to conduct unauthorized activities and avoid detection.
https://www.exploit-db.com/exploits/3381
https://exchange.xforce.ibmcloud.com/vulnerabilities/32697
http://www.vupen.com/english/advisories/2007/0779