knox is a pain in the backside!!
i had many S3 devices, luckily all are still on the old bootloader!! bought an S4 mini few months ago, luckily that was on the old bootloader also, so no knox for any of them, few weeks ago i decided to get the S4, came with knox! sold it, found an old firmware S4, was on 4.2.2 but somehow had the knox bootloader, sold it, bought 4 S4 devices in the space of 2 weeks, all with knox bootloader, ive now given up on S4 and Samsung all together!! ive since then gona back to my old rooted knox free S3 and S4 mini,
no longer will i be buying any more Samsung devices in the future, they can stick it with knox!!
if your reading this thread its probably too late to downgrade your bootloader but i highly advise DO NOT UPGRADE YOUR FIRMWARE!!!
if your rooted keep your old stock firmware thats knox free and keep using custom roms instead!!