VMware ESX Server 2.0.x before 2.0.2 and 2.x before 2.5.2 patch 4 stores authentication credentials in base 64 encoded format in the vmware.mui.kid and vmware.mui.sid cookies, which allows attackers to gain privileges by obtaining the cookies using attacks such as cross-site scripting (CVE-2005-3619).
http://www.vupen.com/english/advisories/2006/3075
http://www.securityfocus.com/bid/19249
http://www.securityfocus.com/archive/1/441825/100/100/threaded
http://www.securityfocus.com/archive/1/441728/100/100/threaded
http://www.corsaire.com/advisories/c060512-001.txt