A lot of Spotify users have reported that the Spotify Free desktop application servers malicious ads on all platforms – Windows, Gnu/Linux and Mac OS X.
Spotify Free Delivers Malware
User reports on Spotify’s forums and on various online communities like Twitter and Reddit have posted that Spotify Free has served them malicious ads. This behaviour has been identified to be caused by the desktop applications which periodically causes the browser to open various sites without the user’s explicit permission. The ads are served from a large network which Spotify may not be able the control, and this is probably one of the reasons why this has happened.
All operating system are affected which includes Microsoft Windows, Gnu/Linux distributions, and Mac OS X. Spotify has responded to the complaints by saying that it is investigating the issue.
Another related incident happened in 2011 when the service posted a public apology after displaying malicious ads to some of its users. This is probably a similar incident that is beyond the control of the administrators as they may not able to choose what types of ads are presented to the individual user based on their profile.
It is very likely that the malicious ads are placed by hackers who have compromised legitimate partners.