As you probably know (you should’ve known 
) there was a vulnerability in ASP.Net discovered that could allow information disclosure. There is already fix to this problem. Read more here:
- http://www.microsoft.com/technet/security/bulletin/MS10-070.mspx
- http://weblogs.asp.net/scottgu/archive/2010/09/28/asp-net-security-update-now-available.aspx
I would recommend to apply those ASAP, according to your security update installation policy. It is especially important, if you haven’t applied any mitigation (described here) before.