Sometimes I get this odd behavior while using Google Chrome:
It appears only sometimes; I can usually get rid of it by refreshing. Is this from some extension? Should I suspect malware? What should I do to figure out what's injecting this stuff?
Also, subjectively speaking, Chrome's felt much slower lately.
edit: there is a rogue extension (source). I will debug.
update: it was JQuery Injector, which has now been removed from the Chrome store.
Here are the possibilities for ads getting popped up:
Extension: As you mentioned, yes! Extensions do result in popping up of such ads. type chrome://extensions in the address bar, and delete all the extensions which you think you didn't install.
Toolbar: Sometimes some random toolbar gets install or we install it thinking it is from trusted sources. Some of these toolbars do pop up ads, which are annoying. These toolbars usually get installed in the form of softwares. Check your programs list and uninstall the one which you think you didn't install and is causing this.
Website based ads: In this case, the ads are shown by the websites themselves and they can't be avoided unless you're using an ad-blocker. If you're getting these ads only on some particular websites, try using an ad-blocker.
In case all the above possibilities fail, then there are chances of some malware, which has many possibilities of getting into.
Try all above methods and see which one helps. Good luck! :)
It's a relatively well-understood problem with some extensions. I'll go in and debug extensions one by one or just redo Chrome.