repository/repository_ajax.php in Moodle 2.2.x before 2.2.5 and 2.3.x before 2.3.2 allows remote authenticated users to bypass intended upload-size restrictions via a -1 value in the maxbytes field.
http://openwall.com/lists/oss-security/2012/09/17/1
http://moodle.org/mod/forum/discuss.php?d=211555
http://git.moodle.org/gw?p=moodle.git&a=search&h=HEAD&st=commit&s=MDL-30792