The remote host is missing an update as announced via advisory SSA:2010-090-03.

https://secure1.securityspace.com/smysecure/catid.html?in=SSA:2010-090-03

New seamonkey packages are available for Slackware 11.0, 12.0, and 12.1 to fix security issues. For more information, see: http://www.mozilla.org/security/known-vulnerabilities/seamonkey11.html