Some users have reported some rather odd behavior with the PlayStation 4 Spotify app. One NeoGAF user noted that Spotify would play a number of random music while they were playing a game.
Okay so I was playing the last main level of Hotline Miami 2 on hard mode and suddenly this weird song comes on. Tonally it fit with the game so I assumed it was a secret of sorts.

Then it changed. And again. And Again. And then I realized Spotify was playing and some random person had linked up to my PS4 and was playing their shit music and I couldn't even turn it off. Spotify wasn't even running on the PS4.

This has never happened on the mobile app or the desktop app, and now I can't even play on the PS4 without the chance that somebody is going to start playing music.

Another user chimed in to note that someone else on the network could access the Spotify playback on any PS4 that was also on the network. The original poster did note that he's at University and boom, the problem seems to have been discovered.

If you are on a shared network, such as one in a public place like college, chances are you run the risk of someone else there playing random music on your PlayStation 4 through the Spotify app. Until this issue is resolved either by Spotify or Sony, you may want to keep the Spotify app uninstalled if you find yourself experiencing similar issues and are on a shared network with others.