Apple has released iOS 5.0 for select models of iPad, iPhone and iPod Touch. This update fixes a large number of critical vulnerabilities in iOS, some of which may lead to unexpected application termination or arbitrary code execution. For more information, see http://support.apple.com/kb/HT4999
The iOS 5.0 is available for the following:
iPhone (3GS and 4 models) currently on iOS 3.0 through 4.3.5,
iPod touch (3rd generation and later models) currently on iOS 3.1 through 4.3.5, and
iPad (any model) currently on iOS 3.2 through 4.3.5
This update is only available through iTunes, and will not appear in your computer’s Software Update application, or at the Apple Downloads site.