Along with Mac OS X 10.6.4, Apple has released a pair of security updates for Mac OS X 10.5.8 Leopard. Apple's and  address 16 different security vulnerabilities.
Several vulnerabilities stem from CUPS (Mac OS X's printing system), including one that would enable an attacker to change CUPS settings were an administrator to visit a maliciously crafted Web site, one that could enable an attacker to issue a denial of service through a malicious get-printer-jobs request, and one that could enable an attacker with access to the CUPS Web interface to read a limited amount of memory from the cupsd process.
Also, the handling of TIFF and MPEG2 encoded files has been improved to avoid arbitrary code execution and program crashes, a problem in iChat that could enable an attacker to upload files to arbitrary locations has been fixed, and an issue that could cause data loss from unmounting maliciously crafted disk images or remote shares has been addressed. Other vulnerabilities that have been targeted relate to Mac OS X's handling of symlinks, Ruby, the SMB file server, and - in Mac OS X Server - SquirrelMail and Wiki Server.
It's worth noting that these updates include Flash Player 10.0.45.2, an outdated version that is vulnerable to security threats. Thus, if you have not yet installed Flash Player 10.1.53.64, you should do so manually after installing this update (see "," 11 June 2010). Fortunately, it appears that the security update does not overwrite the latest Flash Player should you have already installed it.
The of changes provided by the security updates is available on Apple's Web site. The updates are available via Software Update and the Apple Support Downloads page. (Free for both Mac OS X 10.5 Leopard and Leopard Server, 222/380.29 MB)