The remote host is missing an update to squirrelmail announced via advisory DSA 220-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%20220-1

A cross site scripting vulnerability has been discovered in squirrelmail, a feature-rich webmail package written in PHP4. Squirrelmail doesn't sanitize user provided variables in all places, leaving it vulnerable to a cross site scripting attack. For the current stable distribution (woody) this problem has been fixed in version 1.2.6-1.3. The old stable distribution (potato) is not affected since it doesn't contain a squirrelmail package. An updated package for the current unstable distribution (sid) is expected soon. We recommend that you upgrade your squirrelmail package.