I've got players who rely heavily on Leomund's Tiny hut for a "safe" night time rest. I'm alright with them using it to help, but it gets irritating having a wrench thrown into my nighttime attacks. I have found some ways to deal such as Dispel Magic or having something camp them. One time, I even attacked and killed their horses which were outside the hut. I was going to try a burrowing creature but SageAdvice put forward that there IS a floor in the hut. That's when I came across the Phase Spider. So the question:
Could something move into the Ethereal Plane, get to an area that would be inside Leomund's Tiny Hut, and then move back to the Material Plane?