Util.pm in Bugzilla 2.x, 3.x, and 4.x before 4.2.15, 4.3.x and 4.4.x before 4.4.10, and 5.x before 5.0.1 mishandles long e-mail addresses during account registration, which allows remote attackers to obtain the default privileges for an arbitrary domain name by placing that name in a substring of an address, as demonstrated by truncation of an @mozilla.com.example.com address to an @mozilla.com address.
https://bug1202447.bmoattachments.org/attachment.cgi?id=8657861
http://www.securitytracker.com/id/1033542
http://seclists.org/bugtraq/2015/Sep/49
http://seclists.org/bugtraq/2015/Sep/48
http://packetstormsecurity.com/files/133578/Bugzilla-Unauthorized-Account-Creation.html
http://lists.fedoraproject.org/pipermail/package-announce/2015-October/169983.html
http://lists.fedoraproject.org/pipermail/package-announce/2015-October/169946.html
http://lists.fedoraproject.org/pipermail/package-announce/2015-October/168725.html