A pop-up window from a malicious site has opened, should I be worried?

Question

ubuntu

Good day
Recently, I switched from windows to ubuntu. After reading various sources, I decided not to install an antivirus. Today there was a pop-up window, and a very small one. It opened in the background, i.e. I did not see it and worked for about 4 hours further with this pop-up window.
I checked the URL of this site in virustotal, Kaspersky shows that the site is malware.
Browser - Firefox.
There are several questions:
1) Could this window work as a keylogger?
2) Could this window steal cookies\personal data\saved passwords?
3) Could ubuntu have been infected?
4) Is it worth checking with an antivirus now?
5) Is there something worth doing in principle? Change passwords everywhere?

Answer 1

Most likely, it mined bitcoins. If it really was stealing something, it would open and close after sending the stolen data, it would be a pain to keep the window open. But the miner is more likely. And there is also a possibility that there was an advertisement for some kind of casino in this window, but the banner cutter cut it out and only an empty window remained.

Answer 2

The window in the browser does not actually have access to critical data, except if it did not run any plugins (java / flash applet) that allow you to exit the sandbox almost without a request.
Flash, for example, can steal and even replace the keyboard buffer (one of the types of attack, replacing the address of cryptocurrencies with the address of an attacker).

Answer 3

A thousand times such windows have been opened. In 100% of cases, it was, as already mentioned above, an advertisement for a casino or a browser shit (games). It's just that the banner cutter cut it out, and here's the window and it's empty. Probably not worth the fear. You didn’t pick up the malware in 99%, because if you stumble upon malware under Linux, you need to try hard, and if it was a keylogger, then in any case you are already powerless. In short, don’t worry too much, I’m sure it was an advertisement.