A XSS vulnerabiity in ASP.NET could allow information disclosure. The bulletin is a bit vague on the details, but it does mention a problem with headers. Typically, cookie information could be disclosed using XSS attacks. In turn, the cookie information can be used to impersonate an authenticated user.
The script inserted with XSS will inherit all the capabilities the particular user has. For example, a user could be tricked into clicking a link that will escalate privileges for a malicious user. Exploitation typially requires intimate knowledge of the respective web based application.
You will probably consider this problem more severe ("critical") if you use ASP.NET extensively to manage internal applications. However, on the same note first test the page using your specific web based applications.
Other mitigation steps: Disable ASP.NET if not used on your web server.
This patch is not important for workstations and only applies to servers running web sites with ASP.NET support turned on.
I will be teaching next: Defending Web Applications Security Essentials - SANS San Francisco Spring 2020
Oct 10th 2006
1 decade ago