mod/forum/user.php in Moodle 1.9.x before 1.9.16 allows remote authenticated users to obtain the names and other details of arbitrary user accounts by searching for posts.
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=194009
http://git.moodle.org/gw?p=moodle.git%3Ba=commit%3Bh=36b0ddeed45d0751508dcd9fa50f17fda43bae54