Browser.ExecScript() stopped working after updating windows

It turns out Microsoft eventually backpedaled on its decision to kill off .execScript at COM-level. Just install the latest updates for Windows including kb3025390: One of the updates for IE that came after kb3025390 brings back .execScript functionality at COM-level

Note, however, that .execScript is not accessible through IE's javascript anymore. In that context it's gone for good.