i'm a new home owner and was running wire through my attic for a recessed lighting install. i drilled through the top plate and once i broke through i took out my borescope to inspect the surrounding area. i noticed this line that was running across one of the studs and am not sure what it is, so stopped drilling out of, obvious, caution.
more info about home: this is a condo in northeast usa. i have 10 ft ceilings in the upstairs, so after i got through the top plate there is this other layer which you see in the photo below. beyond this wire/pipe is a layer of insulation which has another stud below it (which leads to the switch i need to get to). the photos show the pipe/wire moving horizontally in the direction from the attic to the bedroom upstairs (interior wall).