I've never gave access for this user to my account, though he is somehow using my account at the same time (we can both change songs and devices at the same time). For me it seems like security breach (to be sure, I've changed my Facebook password, which my Spotify account is connected with)
I cannot change device connect password (server responds with error). I cannot disconnect this user either.
My albums and playlists are gone, instead I am left with some Spanish Adele stuff..