The update affects VB6, VBA (including all versions of Office) as well as VBScript!
Microsoft is currently looking into the issue: https://support.microsoft.com/en-us/help/4512488/windows-8-1-update-kb4512488 (look at the last row under the section entitled “Known issues in this update”)
Update:
Microsoft just released a patch for this issue: https://support.microsoft.com/en-us/help/4517298/windows-8-1-update-kb4517298