Popup shows from Avast even after it has been uninstalled

I already found the solution but I am posting this as a question in case anyone needs it too.

Solution: if the popup is appearing when you are using the browser, make sure you delete the browser extension of Avast if you have one. In my case I had a chrome extension of Avast.

So technically, the topic of this thread is incorrect.
Once you finished uninstalling the offending app (extension) the popup stopped.