On a Macbook Air (13-inch, Early 2015) my girlfriend got one of those "upgrade Flash" pop-ups and hit (Continue/Okay/etc?). This may or may not have anything to do with the current problem but ever since, the kernel_task has been hogging the CPU to the point at which the computer is so slow as to be unusable. In Activity Monitor, the % CPU of kernel_task is is a constant 220-450. The CPU load is a constant 75%-90%, although the computer is not getting hot.
Here is what I have done so far. I've reset the SMC and NVRAM/PRAM multiple times. I upgraded to the newest OS, Catalina. I downgraded to the original OS for this laptop, El Capitan. I upgraded and downgraded more than once and each time, the issue remains. The installation of the OSes took forever, as well; been working on this problem for 4 or 5 days now. Oh, and booting in safe mode doesn't help, either. Anyway, two questions:
1) Is it possible for a Flash malware thing to install/configure something in the kernel that remains after re-installing the OS?
2) Any ideas on how to fix this?