There's nothing to worry about and this is old news. These are scare tactics to get you to install Avast/Kaspersky AV. The method of infection they are talking about is a known way that adware can be installed unknowingly by a user and requires downloading and installing a Flash Player update from a pop-up on the web, instead of from the Official Adobe Website. It has been going on for a long time. There's no threat if you don't fall for that gambit.
Their advice for avoiding it is the same as always:
"As always, avoid unusual download links, emails and messages. This program does tend to be served through ads that trick users into downloading, which are commonly found on adult websites, so avoiding that kind of content is a surefire way to steer clear of malicious advertisements."
I believe you do not have Flash Player on your Mac. If you do only download Flash updates from either the Official Adobe website or from within System Preferences > Flash Player > Check for updates. If you do have Flash Player it is unnecessary and you should uninstall it.
If for some reason you do get tricked this way Malwarebytes will take care of it.
There has never been one instance of an actual virus reported on a Mac and if it ever happens it will be major headline news. Which means if it should happen to you the media will beat a path to your door and you will have your 15 minutes of fame! 😎