Knox is certainly to be blamed on Samsung (hence the sec in the file name below), but its a worrying trend nonetheless.
For those rooted users amongst us who are MGG+ original firmware, there are a couple of things you can try to get rid of the Knox annoying messages:
in an adb shell, type pm disable com.sec.knox.seandroid
or perhaps try and freeze Knox apps in TB
Personally, I'm staying on MGA for a while until this calms down a little.