It's not an issue with most smart phones but all it takes is one bad app and this does happen. For most they just factory reset the phone to start over, restore what data they want (no one disagrees about backups.) Then they avoid installing apps. New smart phone users get these issues more often as they try out app after app.
A few months ago we noticed a few different things in my phone's history and search history (porn sites, dating sites and app activity) that I haven't used. Since then we have been keeping an eye on the history and it is a continuing problem. And now, I believe related I am getting emails in primary and spam for similar if not the same sites that show in my history! I'm not visiting these sites and Google is making me look like a lying sexual deviant! Can anyone explain any of this?