While surfing the net using Chrome, I navigated to a page that offered a link to "Smart Package Tracker." I didn't take the bait but the extension attached itself to my browser without permission. The visible effect is to repeatedly display popups whenever the browser is started up.
It isn't listed as a Chrome extension in "tools," and it isn't listed in the apps section of Windows 10. I checked the apps page soon after I picked this up and it showed no recent installations.
Malwarebytes doesn't pick it up, and I also ran Malwarebytes adware program, but no luck. The only thing I haven't tried (short of a Windows clean install) is reinstalling the browser which is likely next, but I'm concerned that it may be buried even deeper than that.