Bugzilla 2.18rc1 through 2.18.3, 2.19 through 2.20rc2, and 2.21 allows remote attackers to obtain sensitive information such as the list of installed products via the config.cgi file, which is accessible even when the requirelogin parameter is set.
https://exchange.xforce.ibmcloud.com/vulnerabilities/22490
http://www.securityfocus.com/bid/14995
http://www.bugzilla.org/security/2.18.4/