The WebService in Bugzilla 3.1.3 allows remote authenticated users without canconfirm privileges to create NEW or ASSIGNED bug entries via a request to the XML-RPC interface, which bypasses the canconfirm check.
https://exchange.xforce.ibmcloud.com/vulnerabilities/42218
https://bugzilla.mozilla.org/show_bug.cgi?id=415471
http://www.vupen.com/english/advisories/2008/1428/references
http://www.securitytracker.com/id?1019968
http://www.securityfocus.com/bid/29038