The iOS updates patch a security vulnerability where, "An attacker with a privileged network position may capture or modify data in sessions protected by SSL/TLS." This means that hackers on a shared network might be able to intercept and read any data you send across it, which could include usernames and passwords, the contents of email messages, or even financial data traveling from you to your banking site.
If you haven't updated yet, I recommend you back up your iPhone or iPad and then install the update as soon as possible. It's a good idea to avoid untrusted or unknown wireless networks, like those found in hotels or other public settings, until you've had a chance to install the patch.
How do I install the update?
- Plug in your iPhone or iPad, or ensure it has more than a 50% charge.
- Touch Settings > General > Software Update.
How can I tell if my device needs an update?
Try performing the update steps above or connect the device to iTunes on a computer. If you need an update, it will be displayed on your device or on the computer.
Note: If you are using a first-generation iPad, be sure you're on iOS 5.1.1, which is the latest OS version for that device. Prior to iOS 5, connecting to iTunes was the only way to do software updates.
Does this security vulnerability affect the Mac?
Yep. Apple plans to release an OS X update very soon. You know, I wouldn't be surprised if Apple releases a patch within the next week or two. Of course, testing to ensure a fix doesn't break anything takes time.