Any enemy with a sword can attack through blocks. I was running away from a gitched zombie pigman who was angry at me when I never attacked a zombie pigman, so I ran up the nether fortress to hide and I placed five blocks, two blocks on top of each other in front of me, two on top of each other at the side of me and one above. I was in a 1x2 area and I backed up to the farthest corner just in case they could somehow attack me, when all of a sudden I take 5 full hearts of damage with full iron armor and I die, not only is this a stupid bug but it made me lose the 67 xp I had.