my question would be what level of "hijacking"??
as it would be closer to hacking, did they get full control for a few seconds, hours?? partial control?? or was only able to access the data feed??
to my next comment, how dose it effect you/defense capabilities?? it really doesn't... there are still manned aircraft, and drones are more a "throw away item" and with the knowledge of Russian hacking ability, counter systems will be getting developed as we speak, what you should ask what was the drones mission?? to "watch" some civil issues or was it armed and sent to kill another us citizen??