Be sure to get this update which fixes some recently talked about vulnerabilities to OSX 10.5.
Java for Mac OS X 10.5 Update 4 delivers improved reliability, security, and compatibility for Java SE 6, J2SE 5.0 and J2SE 1.4.2 on Mac OS X 10.5.7 and later. This release updates Java SE 6 to version 1.6.0_13, J2SE 5.0 to version 1.5.0_19, and J2SE 1.4.2 to 1.4.2_21.
Please quit all web browsers before installing this update.
For more details on this update, please visit this website:http://support.apple.com/kb/HT3581
You can get the update via software update now.