Mozilla Thunderbird before 1.5.0.7 and SeaMonkey before 1.0.5, with "Load Images" enabled, allows remote user-assisted attackers to bypass settings that disable JavaScript via a remote XBL file in a message that is loaded when the user views, forwards, or replies to the original message.

Mozilla Firefox before 1.5.0.7 and Thunderbird before 1.5.0.7 makes it easy for users to accept self-signed certificates for the auto-update mechanism, which might allow remote user-assisted attackers to use DNS spoofing to trick users into visiting a malicious site and accepting a malicious certificate for the Mozilla update site, which can then be used to install arbitrary code on the next update.