This update will add protection against unicode characters being used on signs to overload the chunk and prevent it from saving. As far as I can tell the only way to pull off this exploit is via using a modified or hacked client.

Any player attempting to add illegal characters to a sign will be kicked from the game and the sign will be removed. Keep in mind these signs look totally blank. However looking at them will severely drop your FPS, 5 or so of them is enough to drop your frames a LOT.

http://prntscr.com/ndvre2

There are no options to enable if you are already using the book dupe protection:
(Settings.RemoveBooksNotMatchingCharset: true)

There IS a new option in the config if you have been affected by this dupe that will find existing signs in the world as ones that are already placed will remain in the world unless you find and destroy them, if your server was affected by the sign dupe be sure to enable this line in the config (its off by default)

DestroyBadSignsOnChunkLoad: true