files/externallib.php in Moodle through 2.5.9, 2.6.x before 2.6.11, 2.7.x before 2.7.8, and 2.8.x before 2.8.6 does not consider the moodle/user:manageownfiles capability before approving a private-file upload, which allows remote authenticated users to bypass intended file-management restrictions by using web services to perform uploads after this capability has been revoked.
https://moodle.org/mod/forum/discuss.php?d=313688
http://www.securitytracker.com/id/1032358
http://www.securityfocus.com/bid/74728
http://openwall.com/lists/oss-security/2015/05/18/1
http://git.moodle.org/gw?p=moodle.git&a=search&h=HEAD&st=commit&s=MDL-49994