On Super Bowl Sunday the Dev-Team released PwnageTool 3.1.5 for Mac OSX. PwnageTool 3.1.5 will custom create the IPSW to safely update your firmware to 3.1.3 and still keep your jailbreak and ultrasn0w unlock. Unfortunately for those who have used the blacksn0w unlock (at baseband 05.11.07) will need to stay at 3.1.2, at least for now.

Keep in mind that even the Dev-Team says:

Unless you’ve personally observed a problem with the reporting of your battery percentage, there’s no reason to update to 3.1.3.

For iPhone 3G/3GS users. If you really want/need to update your iPhone firmware to 3.1.3, please be careful when doing so. Any mistake leading you in updating to the official 3.1.3 will lose your unlock and there may never be a way of getting it back.

If you have an iPhone 3GS, PwnageTool will work if you’re currently on 3.1.2 or at least 3.0. PwnageTool will not work on the iPhone 3GS if you’re already running Apple’s official 3.1.3. You’ll have to downgrade to 3.1.2 and if you can’t downgrade because you don’t have your 3GS 3.1.2 hashes on file with Cydia…

As said by the Dev-Team:

you’ll need to sit out the 3.1.3 jailbreak.

Please read the Dev-Team’s “Pre-game show” blog post for more information.

[Dev-Team]