Blizzard Support announced that the v2.4.2 patch has been released. Players simply need to log in to get it:

World of Warcraft patch version 2.4.2 has been released. Players can simply log into the World of Warcraft game client to obtain the latest patch. A complete list of patch changes can be found on our patch notes page: http://www.worldofwarcraft.com/patchnotes/patchnotes.html If you are experiencing any issues with downloading or installing the latest patch, please visit our Patch Issues section for helpful troubleshooting information. We also have our patches available from various Mirror Sites which can be found here. After patching the game, some security software may no longer recognize the game client and prevent connecting to the servers. Players may need to update security software to grant online access to the World of Warcraft (WoW.exe) and World of Warcraft Launcher (Launcher.exe) executables. If you have difficulties reconfiguring your security software you should contact the software manufacturer for assistance.

Log in and grab it.