Apple’s pushing out an iOS update that fixes the PDF exploit that both allowed users to jailbreak their devices in one click but also indicated potentially serious security. If you’re not jailbroken, you should definitely update. If you are jailbroken and would like to stay that way for the time being, you can just protect yourself against the PDF exploit in other ways. The update doesn’t bring any other new features. Plug in your device and click Check for Updates in iTunes to update.