A few days ago, Microsoft released a brand new optional update for Windows 10. KB4512941 is supposedly addressing numerous issues affecting Remote Desktop, Windows Sandbox and other aspects of Windows 10. However, it appears that this update is also causing major high CPU usage issues. According to a lot of reports, Cortana's SearchUI.exe process occupies one whole processor core after applying this update. As such, this will most likely lead to major performance issues. What's really ironic here is that Cortana's search on the desktop does not work anymore. So yeah, this is a bug that can - and will - affect your overall experience. Those that have already downloaded this optional update can either do some changes to their registry or uninstall the update.