They can, but the air-combat drones I posited are remote-piloted drones, which are harder to “crack” than a fully-autonomous one relying on navigational signals would be. Also, a combat drone is nothing more than a weapons platform. It carries very little sensitive tech, so losing one does not have the same impact as losing a surveillance drone, and is also not worth the same effort to bring down as a recon one would be. Plus, a remote-piloted drone can have its control link encrypted, making spoofing and other attacks much more unlikely to succeed. Recon drones have to rely (for now) on signals that by their nature cannot be encrypted. I can’t see much value in the current autonomous drones, save only the really big ones like Global Hawk, which have better stand-off capabilities.
But an air to air drone has to have some way to sense either where it is, or where it's target is, probably both. It needs to know where it is, to be able to handle ques from a parent aircraft. Unless whatever is sending the cues also can independently know where the drone is, and can send relative position cues, rather than absolute target coordinates. (ie. target is 100 nm at 135 degrees magnetic rather than “target is at 110.0159N lon 67.9021W lon) Either way it still needs it's own sensor. Unless it can lanch on a relatively crude heading/range information, and the missile it launches has the sensor.