Here are some interesting links about Silverlight security (I learnt a lot from the first document):
Silverlight security whitepaper:
> http://download.microsoft.com/download/A/1/A/A1A80A28-907C-4C6A-8036-782E3792A408/Silverlight Security Overview.docx
This reading gives you a lot of insight into features like Isolated Storage, Local Messaging, Cross-Site Scripting (XSS), Sandbox, Validate input, https, ….
Shawn Wildermuth’s session at MIX10:
> Securing Microsoft Silverlight Applications
Shawn shows some useful tips like protecting your xap file like any web page.
MSDN library documentation:
As any client technology Silverlight app must be secured so if you are building such app these resources should be a must.