Untrusted search path vulnerability in the installation functionality in ActivePerl 5.16.1.1601, when installed in the top-level C:\ directory, allows local users to gain privileges via a Trojan horse DLL in the C:\Perl\Site\bin directory, which is added to the PATH system environment variable, as demonstrated by a Trojan horse wlbsctrl.dll file used by the "IKE and AuthIP IPsec Keying Modules" system service in Windows Vista SP1, Windows Server 2008 SP2, Windows 7 SP1, and Windows 8 Release Preview.