Bundler before 1.7, when multiple top-level source lines are used, allows remote attackers to install arbitrary gems by creating a gem with the same name as another gem in a different source.
https://security.gentoo.org/glsa/201609-02
http://www.securityfocus.com/bid/70099
http://www.oracle.com/technetwork/topics/security/linuxbulletinoct2015-2719645.html
http://lists.opensuse.org/opensuse-updates/2015-03/msg00092.html
http://lists.fedoraproject.org/pipermail/package-announce/2014-October/140655.html
http://lists.fedoraproject.org/pipermail/package-announce/2014-October/140654.html
http://lists.fedoraproject.org/pipermail/package-announce/2014-October/140609.html