Spotify, the world's most popular music streaming service, has two tiers: a free, ad-supported tier and a Premium, £9.99/$9.99 per month tier. The latter offers offline downloads and unlimited skips of tracks on desktop and mobile while the free tier can only be used to shuffle tracks when listening on a mobile device and adverts play every few songs.

Some users have managed to hack their way to a free Premium account by downloading a Spotify Dogfood app on the Google Play Store, that provides a set of patches to the Spotify APK that then removes the adverts from the free tier. The app doesn't allow for offline downloads or Spotify Connect streaming.

Spotify has since found out about the app and managed to remove it from the Play Store and has even sent what is actually a very polite notice to anyone who used it. The email says: "We detected abnormal activity on the app you are using so we have disabled it, don’t worry — your Spotify account is safe."

Users of the Dogfood app have been told to remove the unauthorised app and install the official one instead. They can still access their Spotify account, including saved playlists and songs, but now have to make do with the adverts or choose to upgrade to the Premium tier. 

Spotify has 159 million users worldwide; 71 million pay for the service while the remaining 88 million are using the free version. It's not clear just how many have been using the Spotify APK hack.