The remote host is missing an update as announced via advisory SSA:2007-085-01.
New mozilla-firefox packages are available for Slackware 10.2, 11.0, and -current to fix security issues. Note that firefox-1.5.x will reach end-of-life next month, so upgrading to the 2.x branch soon is probably a good idea. - From http://developer.mozilla.org/devnews/index.php/2007/03/ 'Note: Firefox 1.5.0.x will be maintained with security and stability updates until April 24, 2007. All users are encouraged to upgrade to Firefox 2.' Since Slackware packages the official Firefox binaries, the Firefox 2 packages in Slackware 11.0 and -current should run on many earlier Slackware versions as well, though there are some known problems with plugins (such as gxine).