Apple has released an updated, iPhone 4S-only build of iOS 5.0.1 (9A406). While there’s no word yet on what the bump brings to the 4S party, The Verge is reporting that hacker MuscleNerd

tweeted an unusual observation about the update: it’s the first official 4S firmware with an accessible encryption key for the main file system, meaning you can browse the file system from a PC unimpeded. Lots of folks are pointing out that this means users will be able to get at Siri’s files without committing piracy, and that could lead to a field day for Siri hacks.

We doubt that’s what Apple has in mind…