I just got Security Update 2006-007 in my Software Update. Think this is in response to the security issues in OS X recently brought to the attention of the general public? Apple's website shows a release date of 11/28, but this is the first I'e seen/heard mention of it.
Security Update 2006-007 is recommended for all users and improves the security of the following components:
AirPort
ATS
CFNetwork
Finder
Font Book
Font Importer
Installer
OpenSSL
PHP
PPP
Samba
Security Framework
VPN
WebKit
gnuzip
perl