CNET quoted an Apple spokesperson saying, "We're aware of this reported issue, we have already developed a fix and it will be available to customers in an upcoming software update." No time frame was given for the update, but it's sure to be soon because the exploit is quite severe.
As we reported yesterday, you could visit a web page with a PDF that contains a program that causes a stack overflow, giving a hacker deep access to your iPhone or iPad. The exploit is possible on any iOS device running OS 3.1.2 or later.
The security hole is actually the same as that used for the JailbreakMe jailbreak for the iPhone 4 and iOS 4, so it stands to reason that Apple's fix will stop that from functioning also. That's how it always goes, though; someone figures out a way in, the manufacturer patches it, then that someone figures out another way in and the manufacturer patches that one too.