From Minecraft Wiki
June 14, 2009
- The server now checks all incoming strings, verifies that they’re all within reasonable limits, and kicks the sender if they aren’t.
- Fixed an exploit where people could crash everyone connected to a server by sending a fake text message.
- The client would gladly attempt to render weird unicode characters, but would crash when trying to look up entry ten thousand in a 256 entry array.
- Fixed an error “Clicked outside the map”.
- "Client 0.0.18a_02 is up" – The Word of Notch, June 14, 2009.