Well I never thought I would see the day Apple has dropped a new firmware for the iPhone 3GS 6.1.6.
They have also release 7.0.6 to the iPhone 4, iPhone 4S, iPhone 5, iPhone 5C, iPhone 5S and iPod touch 5. Like most iOS firmware releases if you have a jailbreak make sure you stay clear of the update. As of now we don’t know if Apple has patched anything in this update.

UPDATE
iOS 7.0.6 is meant to fix SSL connection verification.

“@MuscleNerd: Same advice as last time! Stay away from 7.0.6 if jailbroken, and we’ll update evasi0n7 if possible (this sounds like an important fix!)”