u/Hollimarker

Hi y’all I just replaced a 4 ft fluorescent fixture with a round LED fixture on my closet ceiling. The box, which the fluorescent fixture was not attached to, is just completely loose in the ceiling. So of course when I attach the new fixture to it it just pulls out and dangles from the ceiling. What’s the cheap and easy way to solve this? Can I just spray some foam behind the box to try to lock it in place? There’s framing back there, I can feel it when I try to move the box around. But I’m old and don’t really want to try replacing the box so I can screw it into something.