Cataclysm patch 4.2.2 is now available on all realms!

[Cairenn]

Below you'll find the official patch notes.

Dungeons & Raids

Firelands

• The visibility of Ragnaros' Dreadflame ability has been increased.
• The size of Ragnaros' hit box during the final phase of the Heroic encounter has been increased.

User Interface

• Raid Frames should now remember whether they were shown or hidden upon subsequent logins

Technical

• Players using multiple accounts should now be available to be invited to a Real ID Party.
• Updating a raid roster while in combat should no longer cause a client crash.
• Attempts to purchase Arena Season 10 items should no longer sometimes cause a client crash. (Korea Only)

Source

Notes for all World of Warcraft patches can be found here.