Villagers are able to open iron doors. They seem to do this while in wandering AI, (not at bell sound), or in travelling to bed or workstation.

I have seen this three times, one in survival, twice in creative.

The villagers proceed to enter or not, but leave the iron door open, leading to further possible villager escape. This is clearly a bug, as villagers are not meant to open iron doors.

I have noticed a previous similar report, marked as Resolved. It seems to have reversed the situation, instead of villagers being able to close iron doors, they now open them.

I have this on a video, but it is 4 minutes. Too big, but the weirdest thing is that the iron doors don't close until you give it a redstone update. 

To Recreate:

Put a villager fully surrounded by iron doors,

Proceed to place smith table beneath them.

Place the bed outside.

Let the villager link, then open door with stone button or extremely short (monostable circuit) redstone signal. The door(s) will open, letting the villager think that it can pass, but the door (with a bit of luck, since your villager needs to take half a sec to confirm the new path) will close.

In the travelling to bed, the villager will reopen the door (not realising that it is iron, and unopenable).

He will then race out, leaving evidence; the door will stay open, proving it is not the redstone, but the villager that opened it the second time and not block glitching.

You can also let a villager wander about until it opens a door (less affective as it takes more testing)

This not only makes enclosing villagers in spaces with iron doors impossible, (making you rely on trapdoors, teleporting boats and minecarts, and face it, those things aren't practical for entry and aren't cool unless in secret base), it also allows a bug that keeps open doors open.

Please test and confirm this moderators, upvote so it gets fixed (and puts and end to my impractical entry). I am also sorry for the horrible video quality, (it doesn't like door opening, apparently), and yes, I did redo the first video because it was 10.77 megabytes, just too big.

Thank you!