The iPhone Dev Team released Pwnage Tool 3.1.5 on Monday, only days after Apple released its iPhone OS 3.1.3 update. Pwnage Tool is a utility that "jailbreaks" the iPhone and iPod touch so users can install and run applications that aren't available at Apple's iTunes-based App Store.
While the utility does appear to work, it isn't ready for users that aren't comfortable with terms like "SHSH hashes," and "bootroom."
According to a post on the Dev Team blog, "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."
The jailbreak utility is compatible with the original iPhone, iPhone 3G, iPhone 3GS with early bootroom, original iPod touch, and the second generation iPod touch with early bootroom.
Like any hack, Pwnage Tool could leave you with an iPhone or iPod touch that doesn't work, so don't try jailbreaking your device unless you are comfortable with the process.