Windows 10 1903 build 18362.329 (KB4512941) landed on the production ring as an optional update a short while ago. Some people who installed the optional update are now fighting a problem where their machine has spiked an abnormally high CPU resource consumption issue. The Windows 10 build was a cumulative update that fixed several issues that Windows 10 users had previously been experiencing, only to introduce this new, potentially more serious issue.
Users have been reporting that once the update was installed, CPU usage increased dramatically even when the system was idle. The high usage reportedly comes from Cortana, specifically the SearchUI.exe process that can be found inside Task Manager. Users report that the search functionality in the Taskbar seems to have become non-functional for people suffering from the high CPU utilization issue.
Some of the Windows Insiders fighting the problem logged feedback on the issue in the Windows Feedback Hub. The problem seems to have slipped through in part due to how fast Microsoft sent the update to production. The issue also failed to gather the upvotes it needed to gain additional attention. As of this writing, Microsoft hasn't acknowledged the issue. Some workarounds have been found and to apply them users need to be familiar with and comfortable editing registry keys. The workarounds can be found here and some of them are fairly in-depth.