Thats all the text it shows...
and that text holds a massive clue:
That is not Apple, but a website in India. Everyone gets those and none are real. Neither Apple nor anyone else can "see" or"detect" what is on your computer without your giving express permission for remote access. Any pop-up that says "we detected..." is FAKE.
You can get those from adware but adware itself is a self-inflicted wound. You Mac will caution you not to do ceratin downloads.
Most adware comes from unscrupulous download hositing sites, those that offer free what you know darned well cost money elsewhere. Among common download "bait" types are:
- games
- fonts
- ringtones
- screensavers
- out-of-print instruction manuals from sites ending in .ru
Adware is the little "bonus" the download hosts include to make their money. Typically, alerts like yours were paid-for insertion for by a "security" software creator who cannot sell through regular channels and must resort to trickery. The link would probably take you to one of those sites.
Most useless AV programs will not pick up adware as, as you wisely have observed, can cause more misery on a Mac than they cure. I'm OK with MalwareBytes in that many senior contributors here know and respect the developer from his work in these forums. I have it on my spouse's computer because she is not quite web-aware as I tend to be.
