Hopefully everyone who hasn't rooted yet is no longer using this Knox tripping method. Even with the latest firmware installed,
towelroot.com has the root software. Install the apk open it and click make it rain, wait at least 10 seconds then reboot (even though it says you don't need to), then get
SuperSU from Chainfire and install the apk in the zip file, open the program and update the binary via normal method, if it asks to disable Knox (and you don't need the Knox apps) then disable it. Note: this does not disable the Knox counter, just the apps.
Reboot as SuperSU suggests.
Now that you have root access, you need to get
BusyBox and
Xposed, get the stable version 2.6.1
If you reboot, or power up, into download mode you should see a 0x0 Knox
P.S. you don't need xposed but it has some very nifty modules.