A B767 First Officer reported while taxiing on the ramp a parked aircraft's jet blast blew a container off a tug directly into their path causing them to brake suddenly to avoid collision.

Narrative

The flight from ZZZ1 [Airport] parked at gate X shortly before we pulled into the ramp. It seems that they had one of the engines still running while waiting for the external power. We were taxiing in slowly at a speed of 10 knots when a tug; carrying a belly freight can/ULD (unit load device)" zoomed behind the parked 767-300 airplane with its engine still running. It seems the can was not properly secure to the tug because as it drove behind the parked 767; the jet blast hit the tug and threw the can up towards Taxiway 1 approximately 20 feet in front of us. I pointed out the huge FOD and the Captain quickly brought our airplane to a sudden stop. Without clearance from ground control; the tug driver saw what had happened and zoomed their way back to the can and proceeded to use the tug to ram it away from the taxiway; thus potentially injuring themselves or other people around them. The ramp personnel finally secured the can and cleared the taxiway for us to proceed into gate Y at ZZZ. Improper ULD attachment/secure to tug and tug driving behind and engine running. The tug driver should have waited for the parked 767 to turn engines off and properly secured the ULD TO TUG."