The cert_TestHostName function in Mozilla before 1.7, Firefox before 0.9, and Thunderbird before 0.7, only checks the hostname portion of a certificate when the hostname portion of the URI is not a fully qualified domain name (FQDN), which allows remote attackers to spoof trusted certificates.
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A11162
https://exchange.xforce.ibmcloud.com/vulnerabilities/16868
http://www.redhat.com/support/errata/RHSA-2004-421.html
http://www.novell.com/linux/security/advisories/2004_36_mozilla.html
http://www.mozilla.org/projects/security/known-vulnerabilities.html#mozilla1.7