From Minecraft Wiki
June 27, 2012
12w26a is the thirteenth snapshot released for 1.3.1.
- Monster spawner
- Monster spawners now support extra information for the mobs it spawns. This allows unmodified games to have spawners for special variants of mobs, the player still requires external or modified means to set these parameters, though
- Performance improvements
- Monsters can now spawn on upside down slabs
- Silverfish under the poison effect will spawn silverfish from nearby monster eggs more quickly
11 bugs fixed
- The spruce, birch and jungle wooden stairs can now be crafted.
- Removed the sand and gravel duplication glitch.
- In creative mode, destroying a TNT block no longer drops a TNT block.
- Fixed changing the name of a world, loading that world, saving and quitting it undoing the world rename.
- Fixed the game crashing when it automatically selects the "Scanning for LAN Worlds" item in the server list and you delete it.
- Fixed the arrow representing the player on the map item not pointing in the right direction
- Fixed clicking "Save and Quit" or "Disconnect" twice quickly crashing the game.
- Fixed the multiplayer server fairly regularly dropping all players and showing many NullPointerExceptions in the console every few hours.
- Fixed save files being closed each time the world was auto-saved.
- Fixed placing a piston in front of another which is powered, but not extended, causing the placed piston to become broken and have the same texture on all sides.
- Removed the powered rail duplication glitch.