This document describes the security content of iOS 5.1.1 Software Update, which can be downloaded and installed using iTunes.
For the protection of our customers, Apple does not disclose, discuss, or confirm security issues until a full investigation has occurred and any necessary patches or releases are available. To learn more about Apple Product Security, see the Apple Product Security website.
For information about the Apple Product Security PGP Key, see "How to use the Apple Product Security PGP Key."
Where possible, CVE IDs are used to reference the vulnerabilities for further information.
To learn about other Security Updates, see "Apple Security Updates".

While iTunes for Windows allows you to connect multiple iPod devices simultaneously to the same computer for charging, you cannot sync your data from the computer to all the iPod devices at the same time.

Learn how to troubleshoot certain warning messages that may appear when you attempt to activate your iPhone or iPad.

Your <device> could not be activated because the activation server is temporarily unavailable.
The <device> is not recognized and cannot be activated for service.
iTunes was unable to verify your device.

Use these steps if:

The AirPlay icon doesn’t appear on your iOS device, or iTunes on your computer, after following instructions about how to use AirPlay or AirPlay Mirroring.
or
There are performance issues while using AirPlay streaming or AirPlay Mirroring.

iOS 5.1 introduces Japanese language support for Siri on iPhone 4S.
This article describes how to enable Siri and availability of the feature during the initial rollout.