Ruby on Rails 2.1 before 2.1.3 and 2.2.x before 2.2.2 does not verify tokens for requests with certain content types, which allows remote attackers to bypass cross-site request forgery (CSRF) protection for requests to applications that rely on this protection, as demonstrated using text/plain.
http://groups.google.com/group/rubyonrails-security/browse_thread/thread/d741ee286e36e301?hl=en
http://lists.opensuse.org/opensuse-security-announce/2010-03/msg00004.html
http://secunia.com/advisories/36600
http://secunia.com/advisories/38915
http://www.openwall.com/lists/oss-security/2009/11/28/1