class.phpmailer.php in the PHPMailer library, as used in Moodle 1.9.x before 1.9.16, 2.0.x before 2.0.7, 2.1.x before 2.1.4, and 2.2.x before 2.2.1 and other products, allows remote authenticated users to inject arbitrary e-mail headers via vectors involving a crafted (1) From: or (2) Sender: header.
https://bugzilla.redhat.com/show_bug.cgi?id=783532
http://www.debian.org/security/2012/dsa-2421
http://moodle.org/mod/forum/discuss.php?d=194015
http://git.moodle.org/gw?p=moodle.git%3Ba=commit%3Bh=62988bf0bbc73df655f51884aaf1f523928abff9