HISTORICAL INFO: I posted this on the ASCOM group this morning, and it came out pretty good. So (with a few edits) I'm reporting it here as historical info.

As I noted in the previous post TheSky has its own problems with KB4056898, apparently unrelated to the DCOM Auth change. For all other drivers and API-bearing apps, the DCOM Auth adjustment is enough to get going. Also, note that this Windows security change should have only affected the very few Microsoft customers that are actually using DCOM, and no ASCOM drivers or API-publishing astronomy apps use DCOM. However...

The reason it DID affect these astronomy drivers and apps is that many years ago (10+ years) Software Bisque DID use DCOM, for its Internet Astronomy Client/Server Software (IAS). So TheSky 5/6 registers itself for DCOM with the Windows OS. Back then, in order to provide TheSky 5/6 with the ability to control ASCOM-compliant mounts, the ASCOM Initiative provided a TeleAPI plugin for TheSky that translated the Software Bisque TeleAPI calls into ASCOM. This opened up TheSky's compatibility beyond its built-in telescope control logic to ASCOM. It was quickly discovered that EXE based ASCOM drivers (only) were inaccessible from TheSky/TeleAPI due to DCOM access restrictions coming from TheSky 6. So the drivers, the ASCOM templates, and the installer tools were enhanced to provide DCOM Authentication info as part of the drivers' registration, with the Authentication level set to "None". This was found to be the correct level per Microsoft for connections between EXE processes on the same machine running under the same user. This is the case for ASCOM usage, so for 12+ years, this was fine.

Fast forward to Jan 2018 ... Microsoft changed the requirements for DCOM (which almost no one uses) between processes on the same system under the same user from "None" to "Call". Was it a mistake? Could they have ever caught it in regression testing? Software Bisque CERTAINLY could never have guessed this would happen, nor could the ASCOM people who added in the DCOM Authentication. It is a "perfect storm" of events that got us here.

Will Microsoft "fix" this? It's unclear whether it was an accident or intentional. They publicly say it's a "known issue" and that it will be "resolved" in an upcoming release. Knowing all of the above, I would not classify this as Microsoft's "fault". Again, the reason we can't pulse guide (or even slew through its ASCOM interface) with TheSky X is not related to the DCOM issue, but something else with TheSky X that the KB4056898 triggered. I do not know if it's Microsoft's fault or if there was a latent weakness in TheSky that was triggered by the update.

No one deserves any "blame" in any case. Everyone is doing their best. I will say this: Microsoft has maintained compatibility for applications over the years far better than Apple or the hordes of Linux flavors out there. Of course ancient hardware becomes obsolete and unsupported.