Mobs can hit/attack players through blocks

Can confirm using glass panes to surround the player. In my test, I used zombified piglins

A more recent test I done in 26.20 was to use zombies, the player was surrounded in shelf blocks with no air gaps in the walls in survival to test. I left the ceiling open to grab zombies' attention, then after jumping I ran /setblock ~ ~2 ~ glass to completely surround the player. The player still got attacked and died.