Mozilla Firefox 1.0.4 and 1.0.5 does not choose the challenge with the strongest authentication scheme available as required by RFC2617, which might cause credentials to be sent in plaintext even if an encrypted channel is available.
https://exchange.xforce.ibmcloud.com/vulnerabilities/22272
https://bugzilla.mozilla.org/show_bug.cgi?id=281851
http://www.securityfocus.com/bid/14325