You can add another user to the group afflicted by this problem. I have three Macs, one iMac and two MacBooks, all running the latest version of Catalina, all running Avast Security 14.3, all afflicted by this problem. This most happens overnight and when waking the machine from sleep, web browsers and various other programs are affected. Quitting or force quitting applications does not resolve the problem, and a "clean" reboot cannot be performed as the Mac hangs, which then requires a hard re-boot with the power button.
A case has been opened with Apple in an attempt to diagnose the problem. Web browser cookies and history have been deleted, plug-ins disabled, etc. To no avail. I have run in safe mode without issue. The last test was to create a new "test" user to see if the condition persisted. Given Avast does a low-level install, it runs regardless of user, whereas other programs do not.
This same condition occurred while running logged in as the test user.
I have since uninstalled Avast on my machine - 2015 iMac Retina - and the problem HAS NOT recurred.
If a solution is found, I will re-install. In the mean time, I plan to remove Avast from my other two Macs and consider a competing product.
-Joseph Celona