3.3.8, last time I used it before yesterday's discovery was in February, download was from osx app store
OSX App Store? I wasn't aware that Electrum was available on the Mac App-Store...
The only legit location I know of is the download section at electrum.org (
https://electrum.org/#download)
Is it possible you downloaded a fake version from the app store? Is it still listed on the OSX App Store? Can you provide a link?

I miss-spoke. I downloaded it using brew, which is kind of command line GNU store:
macbook:Downloads arijan$ brew cask list
blender chromium electrum gimp handbrake inkscape inssider onyx processing scribus vlc xquartz