CVE-2009-2422
The example code for the digest authentication functionality (http_authentication.rb) in Ruby on Rails before 2.3.3 defines an authenticate_or_request_with_http_digest block that returns nil instead of false when the user does not exist, which allows context-dependent attackers to bypass authentication for applications that are derived from this example by sending an invalid username without a password.
Date published : 2009-07-10
http://lists.apple.com/archives/security-announce/2010//Mar/msg00001.html