How do adware viruses get in?

Question

Google Chrome

I don’t climb porn sites, I just work on my laptop. The last time I downloaded anything through the browser was June 12th. I haven't inserted a flash drive for almost a month now. I turn on the laptop today, open the browser and see ads, plus the tab itself opens with the site. I bought the laptop in February and, since the moment of purchase, this has not happened. Yesterday I googled a lot related to programming. So I want to understand how this happens?
OS: MacOS Sierra
Antivirus: No

Answer 1

Looks like a browser ad extension.
Unfair extensions can do this in addition to their functionality.
And they can do this with a delay in time so that you do not suspect them.
Try disabling everything and find out which is doing the dirty tricks.

Answer 2

This happens quite often when installing programs :) You put such a figurine, and it shows a bunch of dialogs in which all the checkboxes are already checked :) If you don’t get a grasp and click Next, then the installer will solder a bunch of junk to you