Security Update 2007-004 is recommended for all users and improves the security of the following components:

AFP Client
AirPort
CarbonCore
diskdev_cmds
fetchmail
ftpd
gnutar
Help Viewer
HID Family
Installer
Kerberos
Libinfo
Login Window
network_cmds
SMB
System Configuration
URLMount
Video Conference
WebDAV

For detailed information on this update, please visit this website: http://docs.info.apple.com/article.html?artnum=61798