I recently realized that there were regular clicking activities to some ads from my google account. After a lot of effort for tracking where those clicks originate, i concluded that it is because of the extension "Savefrom.net helper" located here: https://addons.opera.com/en/extensions/details/savefromnet-helper/
It regularly clicks somehow on google ads that redirect you to some russian video websites and it does this without opening any web page etc. I realized it by chance while looking for something else in My Activities in google account.
I just wanted to warn you that this extension is not innocent.
Please do something.