This EXACT same thing happened to me from the update of Flash Player to the bricking of the internet connection to the computer. Luckily I have backup startup drives both for Mojave and Catalina (and older) so I was quickly able to rule out the modem and internet connection. Ruined my day anyway though, I ran Sophos Home and though it found problems they were not fixed. If anyone ever finds a solution it would be good to know. Next Saturday I will wipe my drive and restore the backup. Man this is terrible. The Flash up date was asked for while I was on the CNN website. You can't trust anybody these days.