The remote host is missing an update to mozilla announced via advisory DSA 1053-1. Martijn Wargers and Nick Mott described crashes of Mozilla due to the use of a deleted controller context. In theory this could be abused to execute malicious code.
For the stable distribution (sarge) this problem has been fixed in version 1.7.8-1sarge6. For the unstable distribution (sid) this problem will be fixed soon. We recommend that you upgrade your mozilla packages. https://secure1.securityspace.com/smysecure/catid.html?in=DSA%201053-1