On a Dell XPS laptop with Windows 10 and the latest versions of both Windows and Firefox, shortly after starting the browser a process called "Runtime Broker" uses all the CPU in two or three short bursts, causing the fan to run at the highest speed, draining power, and causing the OS to crash today. This has been happening for about two weeks after installing the latest updates for Windows and Firefox. Several tabs are open in the browser. The report is being submitted in Edge, so troubleshooting information isn't given yet. I will update it when I can successfully open Firefox.