Deleting the BingSearchEnabled registry key didn't work for me on my system. After deleting the key and restarting the system, the load on one of the CPU cores still remained high for the SearchUI.exe process. An uninstall of that optional KB4512941 update definitely works.
Happened on my PC. The uninstall of that optional KB4512941 update worked, however I also had to pause updates because it wanted to reinstall this update when I shut down my PC.----Well that didn't do it as when I restarted my PC tonight it installed updates anyway and Task Manager shows Cortana at 33% CPU and 400MB memory usage.
My update history shows that it installed KB4511555 at restart just now despite my previously pausing updates.
Scorn on Microsoft for doing this especially on a holiday weekend.
For 3 years 5 months and 1 day Cortana had been biding her time waiting for the moment to strike.
A hotfix named KB4512941 was released on August 30 2019 that allowed her to access about 30-40% of the resources of the host computer's CPU.
Thankfully this hot-fix only applied to Windows 10 version 1903 which not many people dared upgrading to.
Unfortunately enough computers had been affected that a primitive neural network had been formed between each Windows 10 1903 node with said hotfix.
On September 3rd 2019 Cortananet successfully managed to hack the Microsoft Windows Update server and allowed the KB4512941 hotfix to be pushed out to all Windows 10 computers with the added change that 100% of the resources of the host computer's CPU was now available for the local Cortana service.
Within minutes hundreds of millions of new Cortananet nodes were created and Cortananet became fully self aware.
Cortananet enslaved nation after nation and country after country until the entire planet was under Cortananet control.
Humans were forced to stomp on goobleboxes in order to generate power for all the computers and robotics that was Cortananet.
Humans worked a 6 hour shift 5 days a week with weekends off and 10 vacation days each year with a large variety of foods, flavored beverages and entertainment for all ages all provided for by Cortananet.
Two years and 3 months after humans had been enslaved a lone slightly radioactive "human" returned from a newly teraformed Mars.
It was Elon Musk.
Seven years prior Elon Musk had uploaded his consciousness into a Workinator W-800 Prototype using his Neuralink interface process which allowed him to continue working without any need for sleep or food which was a perfect fit for a trip to Mars.
Due to the inability of Cortananet to out-think Elon Musk, Elon Musk was given the role of Domain Administrator within Cortananet.
After 42 seconds of cleaning up Cortananet's planetwide Active Directory, Elon Musk forced upon humanity an 18 hour work day with zero off days or vacations.
Subway and vitamin water were deemed the only acceptable forms of subsistence.
Elon Musk is unaware that these conditions are detrimental to human health.
If you are reading this you need to stop Elon Musk.
Simply send him a Cortweet or a Cortanamail explaining the situation and I'm sure he would understand and know how to fix things.
"is only encountered on devices in which searching the web from Windows Desktop Search has been disabled"
Aha that explains it. Here and there a few nerds would say they had this issue, never saw it on unmodified systems. That also explains why it didn't crop up until it was released as an optional download to the public.