Last Tuesday, Apple has released iPhone OS 3.1.3, that brings a number of bug fixes and security fixes. As mentioned in earlier post, this version update is primarily for bug fixes with no major feature. If you’re using jailbroken iPhone, personally I do not recommend to spend effort to go through the whole jailbreak procedures again for upgrading your iPhone.

If you like to upgrade with the latest iPhone OS update, you can use PwnageTool 3.1.5 to upgrade and jailbreak your iPhone. Unlike redsn0w, PwnageTool allows you to create a custom firmware file (i.e. IPSW) and preserve the baseband of firmware 3.1.2. That means, via the custom firmware, even you upgrade to iPhone OS 3.1.3, you can still use unlock tool (e.g. ultrasn0w) to unlock the iPhone. (Note: for bootrom with baseband 04.26.08 only). Please read the following advice from iPhone Dev Team carefully:

iPhone 3G and 3GS unlockers should always be very wary to update their firmware. This is no exception. If you make a mistake along the way you may find yourself updating to official 3.1.3 in which case you will lose your unlock, possibly forever.

iPhone 3Gs users (regardless of unlock) should stay away from this and all 3.1.3 jailbreak tools unless you know you have your “SHSH hashes” backed up via Cydia. That’s because if you make a mistake you may find yourself stuck at official 3.1.3 with no way to jailbreak or come back down to 3.1.2 to jailbreak.

If you really truly feel that you need to update, this version creates a custom 3.1.3 IPSW for you to restore to on your iPhone 2G, iPhone 3G, iPhone 3GS with early bootrom, iPod Touch 1G, and iPod touch 2G with early bootrom. If you don’t know if you have an early bootrom or not, please avoid updating until you learn more.

If you have accidentally (or intentionally) upgraded to firmware 3.1.3, PwnageTool will not work for you. You’ll have to downgrade to iPhone OS 3.1.2 (provided that you have “SHSH hashes” back up via cydia) before you can apply the jailbreak. If downgrade is not an option, you will need to stay with 3.1.3 and wait for another jailbreak solution.

For iPhone 3GS using blacksn0w to unlock, please remember to stay with firmware 3.1.2. You should not upgrade to iPhone OS 3.1.3, otherwise, you will lose the unlock.

If you understand the risk of jailbreaking iPhone OS 3.1.3, you can download PwnageTool 3.1.5 from here