Looks like Apple and Google developers or testers spend a lot of time surfing Boy Genius Report. Going through their logs, BGR found traces of both iPhone OS 3.1.3 and iPhone OS 4.0.
However, don’t get pretty excited yet, browser user strings can be easily faked and you can almost add anything you want to it. If you are a programmer, I don’t even have to tell you that. However, if you want you can do this yourself too, read our earlier tutorial on Emulating mobile browsers in Firefox, and you can very well have a browser for iPhone 5.0 or iPhone OS 100.0.
On the hindsight, this might be a trick played by someone, since quite recently BGR picked up the Nexus One browser string from their logs. So all is well until you see some more specific news coming out for an update to the iPhone OS. Till then this is definitely fake, try fooling someone using the emulating trick from our earlier tutorial ;-).