The problem (as ever) lies with PDF documents and has been identified by Germany's Federal Office for Information Security. Downloading or clicking a link to an infected PDF can breach your device's security, allowing attackers to "gain administrator rights and get access to the entire system".
That means your passwords, calendars, email and other things you'd rather keep away from prying digital thieves.
The issue could affect devices including the iPhone 3G, iPhone 3GS, , iPad, and , running software versions up to and including iOS 4.3.3. The Bonn-based security agency says it "cannot exclude" the possibility that other versions -- including the as yet unreleased iOS 5 -- are also affected.
That means that unless Apple pulls its finger out and fixes the problem, the iPhone 5 could be released with a security flaw from day one, which would be the opposite of good. Ungood.
The jailbreak community has developed a fix for the security flaw, but it requires you to jailbreak your iOS device to make it work. So, amazingly, until Apple releases an update that resolves the problem, jailbroken devices are actually a wee bit safer. Apple does not allow antivirus apps in its App Store.
A spokesman for Apple Germany has told Associated Press that Apple is aware of the warning that has been issued, but would not comment on it.
Update: Apple has been in touch with the following comment: "Apple takes security very seriously, we're aware of this reported issue and developing a fix that will be available to customers in an upcoming software update." Fingers crossed we don't have long too wait.