The default configuration of SGOS in Blue Coat ProxySG before 6.2.16.5, 6.5 before 6.5.7.1, and 6.6 before 6.6.2.1 forwards authentication challenges from upstream origin content servers (OCS) when used in an explicit proxy deployment, which makes it easier for remote attackers to obtain sensitive information via a 407 (aka Proxy Authentication Required) HTTP status code, as demonstrated when using NTLM authentication.