Apple released a new update iPhone OS 3.1.3 with minor fixes, however, users who have a jailbroken iPhone or iPod Touch will lose all their changes it they update to iPhone OS 3.1.3.
Hot on the heels of the new update, a jailbreaking software called redsn0w was updated to support iPhone OS 3.1.3 for iPhone and iPod Touch. The redsn0w team released a new update, version 0.9.4 to support jailbreaking and unlocking for iPhone OS 3.1.3.
However, unlocking is currently available for only iPhone 2G users, so it is advisable to iPhone 3G and 3GS users to stay away from the update for sometime, or else they will be carrier locked till an unlock jailbreak is available.
To jailbreak iPhone OS 3.1.3 on an iPhone or iPod Touch, update iTunes to the latest version and update the firmware to OS 3.1.3. After that you can download redsn0w and follow the instructions listed out by Redmond Pie. redsn0w 0.9.4 is available as a download for both Windows and Mac OS X.