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Opening a Shell window registered under Control Panel starts new explorer.exe process on Windows 10 after recent updates

Prabodh Mairh 11 Reputation points
2020-11-03T07:18:57.65+00:00

We have a Shell window registered under Control Panel. We use Win API CoCreateInstance to create an instance of it on the local system. Earlier this used to use the default explorer.exe process (the one used for tray icons and taskbar). But after installing the recent updates KB4579311 and KB4577671 on Windows 10, we see that a new explorer.exe process is started with /factory switch. It looks something like this in the task manager. 

C:\windows\explorer.exe /factory,{5BD95610-9434-43C2-886C-57852CC8A120} -Embedding

We also observed that now launching Control Panel always runs it in a separate explorer.exe with a similar "/factory" switch.
There are also couple of new registry keys which look related - these do not exist on machine without updates. 

HKEY_CLASSES_ROOT\CLSID\{5BD95610-9434-43C2-886C-57852CC8A120}
HKEY_CLASSES_ROOT\CLSID\{5BD95610-9434-43C2-886C-57852CC8A120}\LocalServer32

My question is - Has something changed in these recent updates that causes this behavior? Is there a way via some preference or registry settings to force the default explorer.exe to be used?
Is this a conscious design change to always use a separate explorer.exe for opening Control Panel and all the programs registered under it? If so, is there some documentation update or articles that provides more insights into this?

Windows 10
Windows 10
A Microsoft operating system that runs on personal computers and tablets.
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  1. Karlie Weng 15,761 Reputation points Microsoft Vendor
    2020-11-04T08:14:17.117+00:00

    Hi @Prabodh Mairh ,

    Would this just a separated Explorer.exe, so if one crashes the other stays alive?

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    Karlie

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  2. Prabodh Mairh 11 Reputation points
    2020-11-04T08:44:24.33+00:00

    @Karlie Weng Our application was written to run in proc the main explorer.exe (the one associated with taskbar and desktop). In the event of the explorer.exe getting crashed, everything started on a clean plate anyway, but it worked. But now the things are broken since part of it runs on a separate explorer.exe and we never supported that scenario - no inter process communication is built in.

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