The remote host is missing an update to iceweasel announced via advisory DSA 2488-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%202488-1

Several vulnerabilities have been discovered in Iceweasel, a web browser based on Firefox. The included XULRunner library provides rendering services for several other applications included in Debian. CVE-2012-1937 Mozilla developers discovered several memory corruption bugs, which may lead to the execution of arbitrary code. CVE-2012-1940 Abhishek Arya discovered a use-after-free problem when working with column layout with absolute positioning in a container that changes size, which may lead to the execution of arbitrary code. CVE-2012-1947 Abhishek Arya discovered a heap buffer overflow in utf16 to latin1 character set conersion, allowing to execute arbitray code. Note: We'd like to advise users of Iceweasel's 3.5 branch in Debian stable to consider to upgrade to the Iceweasel 10.0 ESR (Extended Support Release) which is now availble in Debian Backports. Although Debian will continue to support Iceweasel 3.5 in stable with security updates, this can only be done on a best effort base as upstream provides no such support anymore. On top of that, the 10.0 branch adds proactive security features to the browser. For the stable distribution (squeeze), this problem has been fixed in version 3.5.16-16. For the unstable distribution (sid), this problem has been fixed in version 10.0.5esr-1. We recommend that you upgrade your iceweasel packages.