The classes in the System.Reflection namespace and with System.Type, enable us to obtain information about loaded assemblies and the types defined within them, such as classes, interfaces, and value types. Reflection can be used to create type instances at run time, and to invoke and access them.
Depending on the .Net framework version, the use of Reflection could represent a major security risk.
The risk with using Reflection is that the original application code could be replaced by malicious code. The use of .NET framework 4 and on offers a higher level of protection since only trusted code can use reflection to access security-critical members. Furthermore, only trusted code can use reflection to access nonpublic members that would not be directly accessible to compiled code. Finally, code that uses reflection to access a safe-critical member must have whatever permissions the safe-critical member demands, just as with compiled code.
For other .NET framework versions beneath version 4, there are important recommendations to follow
Avoid writing public APIs that take MethodInfo parameters
Avoid it especially for highly trusted code. Such APIs might be more vulnerable to malicious code. For example, consider a public API in highly trusted code that takes a MethodInfo parameter. Assume that the public API indirectly calls the Invoke method on the supplied parameter. If the public API does not perform the necessary permission checks, the call to the Invoke method will always succeed, because the security system determines that the caller is highly trusted. Even if malicious code does not have the permission to directly invoke the method, it can still do so indirectly by calling the public API.
using ReflectionPermission class
To discover information about nonpublic members, callers must have the ReflectionPermission that represents the ability to obtain type information. Without this permission, code cannot use reflection to obtain information about nonpublic members (even of its own class) through the Get methods on Type, Assembly, and Module.(MSDN)
To use reflection to invoke methods or access fields that are inaccessible according to the common type system accessibility rules, the code must be granted the ReflectionPermission for member access.
security policy deny ReflectionPermission to code that originates from the Internet
Because ReflectionPermission can provide access to non-public types and members,it is recommend that you do not grant ReflectionPermission to Internet code, except with the ReflectionPermissionFlag.RestrictedMemberAccess flag. RestrictedMemberAccess allows access to non-public members, with the restriction that the grant set of the non-public members must be equal to, or a subset of, the grant set of the code that accesses the non-public members.
MSDN, "ReflectionPermission Class" available at http://msdn.microsoft.com/library/system.security.permissions.reflectionpermission(v=vs.110).aspx