The title says it all.

Sneaking should prevent you from falling off a block. In 1.4.3 it doesn't prevent you from falling off a chest. Might be related to the fixed hitbox of chests.

I have seen that enderchests have been updated too, so it might happen there too. Atm you can sneak on enderchests in 1.4.3, which contradicts the behaviour of normal chests

Also affects soul sand.