It's a good news for all ASP.NET developers. Microsoft has released v.4.0 of AntiXSS library. XSS is a type of website vulnerability and can be found in many websites. 
The Microsoft Anti-Cross Site Scripting Library V4.0 (AntiXSS V4.0) is an encoding library. This library is designed to help developers protect their ASP.NET web-based applications from XSS attacks. It differs from most encoding libraries in that it uses the white-listing technique -- sometimes referred to as the principle of inclusions -- to provide protection against XSS attacks. This approach works by first defining a valid or allowable set of characters, and encodes anything outside this set (invalid characters or potential attacks). The white-listing approach provides several advantages over other encoding schemes. New features in this version of the Microsoft Anti-Cross Site Scripting Library include:- A customizable safe list for HTML and XML encoding- Performance improvements- Support for Medium Trust ASP.NET applications- HTML Named Entity Support- Invalid Unicode detection- Improved Surrogate Character Support for HTML and XML encoding- LDAP Encoding Improvements- application/x-www-form-urlencoded encoding support 

Supported Operating Systems:Windows 7;Windows Server 2003;Windows Server 2008;Windows Vista;Windows XP
OS: Microsoft WindowsSoftware: .NET Framework 3.5

download here:
http://www.microsoft.com/