The remote host is missing an update as announced via advisory SSA:2008-191-03.

https://secure1.securityspace.com/smysecure/catid.html?in=SSA:2008-191-03

New seamonkey packages are available for Slackware 11.0, 12.0, 12.1, and -current to fix security issues. More details about the issues may be found here: http://www.mozilla.org/projects/security/known-vulnerabilities.html#seamonkey