Levers can be placed on Iron doors, causing them to be dropped when activated.

Levers can be placed on both the top and bottom halves of Iron doors, causing them to be dropped when activated, and the door to open and close very quickly.

Please note this issue may exist in versions before 21w13a, but it has been discovered in this version.

Video: https://youtu.be/OgGF7aSu91c