I haven't seen such notification windows with any other browser.
Some weeks ago there started to appear small notification windows in right bottom corner - mostly kind of adds.
My first reaction was malware or virus but this doesn't appear to be the problem.
When clicking in this small windows settings icon - it opens Opera settings, block adds in upper position.
I have switched blocking on, cleared exceptions but these notifications still continue to appear.
Any idea how to stop this Opera behavior?