They are now 1 block high (or less), they used to be the same height as fences. This is really bad for animal pens and breaks other contraptions, such as fishing farms.
It's possible to jump on a cobblestone wall.
Mobs and player can pass through stone wall.
Cobblestone And Mossy Cobblestone Walls Are Not Acting As Normal
Cobblestone Wall now only one block high
V1.11.1 Players, Horses, and Llamas can go over cobble fence
Stone Walls Can Be jumped over