WordPress allows remote attackers to determine the existence of arbitrary files, and possibly read portions of certain files, via pingback service calls with a source URI that corresponds to a local pathname, which triggers different fault codes for existing and non-existing files, and in certain configurations causes a brief file excerpt to be published as a blog comment.
http://www.securityfocus.com/archive/1/458003/100/0/threaded
http://www.securityfocus.com/archive/1/457996/100/0/threaded