I've been getting popup ads for a memory-cleaning app on my S7. I've been in the middle of something - the last time I was using Chrome - when without warning, a recorded voice came from the speaker and said out loud, "Warning - your system is critically low on memory. Please go to the device settings to perform maintenance." Or, pretty close to that. At the same time it opened up Google Play Store and directed me to the listing for this app which, I presume, cleans up your RAM for you. Pressing the home button does nothing to stop it once it starts, though thankfully I'm free to control it after that. It's happened three times now - anyone know how to prevent this?