Bugzilla 2.23.3 through 2.22.7, 3.0.x through 3.3.x, 3.4.x before 3.4.12, 3.5.x, 3.6.x before 3.6.6, 3.7.x, 4.0.x before 4.0.2, and 4.1.x before 4.1.3 allows remote attackers to determine the existence of private group names via a crafted parameter during (1) bug creation or (2) bug editing.
https://exchange.xforce.ibmcloud.com/vulnerabilities/69034
https://bugzilla.mozilla.org/show_bug.cgi?id=653477
http://www.securityfocus.com/bid/49042
http://www.debian.org/security/2011/dsa-2322