Just one day after iTunes 9.0.3 is released, Apple has released iPhone OS 3.1.3. This update is for iPhone, iPhone 3G, iPhone 3GS, and iPod Touch. It contains a few bug fixes, but no new features, since 3.1.2.

To update, just connect your device to your computer. If iTunes doesn’t launch automatically, open it. If you are not prompted automatically to update, then just click “Update”, in your device summary. Then, just follow the above prompts.

WARNING: The iPhone Dev Team has advised users with jailbroken devices to hold off on this update, until then can confirm it is safe, and they are able to update their jailbreak tools (redsn0w and Pwnage Tool).