Malware is found only by the Opera browser! There are no such warnings in Chrome, Safari, or Firefox

If one of Opera’s list providers has identified malware on a website, but other browsers have missed it, that is a good thing for Opera, not a bad thing. Other browsers have failed to detect it.

You can see which list provider has detected the malware by clicking the “Why was this page blocked?” link on the warning page in Opera. You can report it to that blacklist provider if you believe it to be a mistake.