The remote host is missing a critical security patch or upgrade.
The remote host is using SeaMonkey. The installed version of SeaMonkey contains various security issues, several of which are critical as they can be easily exploited to execute arbitrary shell code on the remote host. The version of SeaMonkey is vulnerable to multiple denial of service attacks, overflows, information disclosure, privilege escalation, and other issues. An attacker exploiting these flaws would need to be able to convince a user to browse to a malicious URI.