Please REMOVE wlanext.exe
I had been disturbed by the high CPU usage of wlanext.exe for nearly two years, just like many other users with the same problem.
This program keeps starting and running when Windows starts, even I disabled WiFi module.
So a few days ago I DELETED wlanext.exe in C:\Windows\System32 (with restore point), and it turned out that Windows runs NORMALLY without this annoying program! Since then I never have any mistake on WiFi or any.
I think wlanext.exe does nothing but takes 25% of CPU. :-)
Therefore, please REMOVE wlanext.exe!
Windows Version: Windows 10 Pro 1709 (Build 16299.3xx → 16299.402)