Issue:
Iron doors exist as a form of security door, only openable via redstone and harder to destroy than a wooden door (without tools) During my play in a solo survival world, I was low on health and ran inside while a zombie was chasing me, upon the iron door closing behind me, I turned to see the zombie damaging the door. I thought perhaps this was merely a visual bug and the zombie would be incapable of actually destroying the door, however, I was soon proven wrong once the zombie broke the door down.
It should be noted that iron doors are intended to be mob proof. This bug eliminates this

Steps to reproduce:
Build a home with an iron door as the entrance
Set difficulty to Hard
Spawn a zombie or let one spawn naturally
Lure it to your door and make sure it closes behind you
Observe as the zombie easily breaks the door down

Expected Result:
The zombie stops at the door and is unable to proceed

Actual result:
The zombie destroys the door effortlessly and continues pursuit of the player.

Edit:
Looking more and more at how incompetent the staff on this site seems to be, I've attached a video PROVING this bug to exist. If this continues to be ignored, I'm going to the devs directly. I've had it.