Thanks for a quick reply, DavidR.
“Are you sure this is a browser, as in the Avast Secure Browser (ASB) ?”
Yes. I took a screenshot from Revo Uninstaller Pro, showing it’s a ‘New Program’. (While Avast shows up there, too, I’ve been using it for a lot of years.)
“I did a manual Program update from the user interface of Avast Free to the version in my signature and it wasn't installed”
Same here, the way I’ve always done it: Check for Update …buzz-whir… Click to Restart.
The difference this time, though, is the Finish screen came up very quickly, and a strange browser window opened.
“If this truly is the ASB browser and not the browser add-on/extension (Avast On-line Security) …”
I had to search for it but I did find the Browser Extension section in Avast and yes, Avast On-line Security is showing up there, also. Next to my browser (Firefox) is a green button that says “Enable Extension”.