The announcement was made via his Twitter account:
I now have a binary that untethers 6.1.3. Needs some more work though.
While a tethered jailbreak for iOS 6.1.3 is currently possible for users with the iPhone 4, iPhone 3GS, or iPod touch 4G, winocm has only confirmed that he has his code running on an iPhone 4:
I have my own code running inside the iOS 6.1.3 kernel on iPhone 4.
Notably, he says it's not useful for iOS 7.
It’s not useful on iOS 7. I don’t care about iOS 7. Other people are taking care of iOS 7.
We'll let you know as soon any more details come into light. Please follow iClarified on Twitter, Facebook, Google+, or RSS for the latest.