The last update let you place ivy on the back of stairs. Ivy, when attached to a regular block like a piece of cobble, will usually do so without a problem. If there is an upside down stair overhang, it will place with it's normal wall attachment graphic. When you try to put it on a block that is overhung by a right side up stair though, it will not place. (Since the bottom of a right side up stair looks like a normal block you'd expect it to latch to the bottom of the stair.)

Attached is ivy below a normal block overhang (left), ivy below a upside down stare(right), and no ivy under a right side up stair (it won't place). Ideally it would place like the left example, right?