I suspect the controller is defective or has some loose connections. Most often if DC power is disrupted and then goes back back on in a couple of seconds the outside light will come ON.
I would inspect the connections around the controller board wherever that is located haha...
You could always just pull the main 12VDC fuse in the panel that is controlling this and use that for your turning on and off as needed until you find the real problem...
Those outside 8-inch DC lights are sometimes called scare lights. You should be able to find a named fuse zone in your fuse panel that only controls those lights. My trailer has two installed up high on each side of the trailer close to the rear of the trailer. I imagine the DOT RUles would prevent any of those light installed on the rear wall of the trailer just for the reason you are stating here that come on by themself sometimes... That would be a big DOT Safety violation if this happened being pulled down the public roads...
My 2008 Flagstaff has them installed like shown here in this on-line google photo. Mine are controlled by a standard ON-OFF switch from inside the trailer... I am assuming this is the security lights you are referring too...

Roy Ken