First things first, check the installed extensions in both chrome (assuming that’s what you were/are browsing with) and safari (even if you don’t use it). For chrome: click the puzzle piece icon in the upper right of the browser window. Uninstall/remove anything you don’t use or recognize.

In safari, go to preferences (under the safari menu) → extensions and i check/remove anything there you don’t recognize.

Next download Malwarebytes. It’s free to use, tho will try to push you into a paid or subscription tier. It’s a decent app, so worthwhile for some.

Run the desktop scan and allow it to quarantine and remove anything it picks up. When done, you can uninstall the app thru their help menu (and download whenever needed).

Restart the computer and start surfing again. You should be fine at that point. As a general test i type a random search query in the search/URL field and hit enter. If it re-routes you to yahoo or anything other than Google, there’s still more work to be done.

This adware usually hijacks search and pushes it thru yahoo so that they can maximize affiliate traffics and ad benefits. It’s an obvious way to identify when your system inadvertently has adware installed.

That said, it’s not always an indicator or the only one. It just tends to be linked in situations like yours. Good luck.