Bugzilla 2.19.3 through 2.20 does not properly handle "//" sequences in URLs when redirecting a user from the login form, which could cause it to generate a partial URL in a form action that causes the user's browser to send the form data to another domain.
https://exchange.xforce.ibmcloud.com/vulnerabilities/24821
https://bugzilla.mozilla.org/show_bug.cgi?id=325079
http://www.vupen.com/english/advisories/2006/0692
http://www.securityfocus.com/bid/16745
http://www.securityfocus.com/archive/1/425584/100/0/threaded