Apple has just released the iOS 4.0.2 software update for the majority of their iDevices. But, unlike many other updates in the past, this one's primary focus is one thing, and one thing only: to patch up that pesky malicious PDF situation that shot up a couple weeks back. The update doesn't really do anything other than that, despite the fact it comes in two variations: 4.0.2 and 3.2.2. (for the iPad).
The update itself will remove your jailbreak, if you are currently jailbroken. And, if you used the site jailbreakme.com, you should expect that not to work anymore, either. We know that Apple's removal of jailbroken software from their iPhones/iPods/iPads isn't new, especially with software updates, and we should all expect the jailbreakers out there to take care of the situation on their side in no time. So, if you want to keep your jailbroken iDevice the way it is, go right ahead and don't download this. But, if you want to patch up that huge security hole, and can wait to get jailbroken again, then you probably want to get to downloading.