On periodic basis we release updates for Windows Azure Guest OS. These OS are generally used by cloud services deployment (mainly PaaS).
Windows Azure supports three Guest OS families.
A very helpful Link to keep track of any changes or update:
http://sxp.microsoft.com/feeds/3.0/MSDNTN/WindowsAzureOSUpdates (Please subscribe it)
Other Useful links:
Managing Upgrades to the Windows Azure Guest OS
Configuring Settings for the Windows Azure Guest OS
Overview of Windows Azure Host OS Updates
Windows Azure Guest OS Releases and SDK Compatibility Matrix
How to: Manage Upgrades to the Windows Azure Guest OS
Support Escalation Engineer
Windows Azure Technical Support