The remote host has a web browser installed that is vulnerable to multiple attack vectors.
Versions of Mozilla Firefox prior to 1.7.13 are affected by various security issues, several of which are critical as they can be easily exploited to execute arbitrary shell code on the remote host. Additionally, these versions are affected by 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 Mozilla user to browse to a malicious URI.
Upgrade to version 1.7.13 or later.