CVE 2006-6104
The System.Web class in the XSP for ASP.NET server 1.1 through 2.0 in Mono does not properly verify local pathnames, which allows remote attackers to (1) read source code by appending a space (%20) to a URI, and (2) read credentials via a request for Web.Config%20.
See the 
CVE page on Mitre.org
for more details.
