It's same way as .net framework. If updates exist for 1.1, the full 2.0 will not fix the security of the 1.1 and 1.1 is needed too ... IMHO, for MSXML we must keep all differents version, no just the MSXML6.0 ... Reading http://www.microsoft.com/technet/security/...n/ms06-061.mspx I have understand the KB924191 is for XML version 3.0 , 4.0 and 6.0.