theme/yui_combo.php in Moodle 2.3.x before 2.3.2 does not properly construct error responses for the drag-and-drop script, which allows remote attackers to obtain the installation path by sending a request for a nonexistent resource and then reading the response.
http://openwall.com/lists/oss-security/2012/09/17/1
http://moodle.org/mod/forum/discuss.php?d=211560
http://git.moodle.org/gw?p=moodle.git&a=search&h=HEAD&st=commit&s=MDL-35168