A Matter of Security
There are quite a few security enhancements provided with Silverlight 5. On the networking side, the most important is the post-beta addition of the WS-Trust specification to the web service stack. WS-Trust is an open standard that facilitates secured message exchange using the widely accepted SOAP messaging format. It includes provisions for establishing security tokens and brokering trust relationships. This addition provides far more flexibility and security for Silverlight networking, especially within the enterprise.
Using a combination of policies and registry key settings, trust for Silverlight applications can now be established within the browser. This means that features such as hosting a web control or accessing the file system, which were previously limited to out of browser (OOB) Silverlight implementations, can now be performed by the application from the web browser. While the previous versions of Silverlight limited file system access to the special folders such as documents and pictures, the new version provides full file system access.
For trusted applications that are running out of the browser, the new framework provides true child windows. These are independent windows managed by the OS that can be moved, sized, and closed independently of the main window. For LOB applications, this is an incredibly powerful feature because it will allow elements of a dashboard to be detached and pinned as separate windows.