Apple just released the Mac OS X 10.5.8 update, which includes security fixes:
One of the fixes is for a heap-based buffer overflow in the ColorSync component (which handles the parsing of ICC profiles). Limited details are here:
This vulnerability could likely be used to execute arbitrary code in contexts such as Safari browsing to a malicious page. Mail clients (both web-based and local client based) might make an interesting target.
This was discovered because the test case for my earlier LittleCMS (lcms) vulnerabilities happens to crash Safari when you hit it: