Blizzard has released a new patch for World of Warcraft. The 1.12 patch updates the 1.11.2. It is 16MB in size and has new features such as Cross-Realm Battlegrounds and World PvP. There are some general changes which have also been incorporated.
According to the official World Of Warcraft website:
For the first time in the history of World of Warcraft, you will be able to face off against players from other realms in the Battlegrounds. PvP Battlegrounds link Alterac Valley, Warsong Gulch, and Arathi Basin so that players from several realms will be combined into one huge matchmaking pool. Replenish your mana, sharpen your blades, and get ready for some brand-new challengers!