According to a user posting on Spotify Community, the malware causes ads to launch "and keep on launching" the computer's default browser to different sites lined with viruses (via The Next Web). Multiple macOS and Safari users have confirmed the issue to be happening on Apple systems.
It's not clear yet what's causing the issue, but multiple confirmations of its connection with Spotify Free have surfaced on Twitter, with users reporting that malware ads have appeared on both Mac and Windows platforms. Spotify has responded to a few users on Twitter and appears to be looking into the issue, but has yet to make an official announcement.There's something pretty alarming going on right now with Spotify Free. This started a several hours ago. If you have Spotify Free open, it will launch - and keep on launching - the default internet browser on the computer to different kinds of malware / virus sites. Some of them do not even require user action to be able to cause harm.
I have 3 different systems (computers) which are all clean and they are all doing this, all via Spotify - I am thinking it's the Ads in Spotify Free. I hope this has been noticed and Spotify staff are fixing it - fast. But it's still puzzling something like this can actually happen.
One Mac user was running OS X El Capitan 10.11.6 on a mid-2014 MacBook Pro when the ads in Safari began popping up.
PSA: uninstall Spotify free, their ads are plagued with malware right now. pic.twitter.com/DUOqDrnDUZ - Volp (@VolpRS) October 5, 2016
Spotify eventually commented on the problem, saying "we sincerely apologize to any users affected. We'll continue working hard to ensure this does not happen again and that our users enjoy Spotify securely and in confidence."
Article Link: Spotify Free Desktop Users Facing Malware-Filled Ads on Mac and Windows