Apple has rolled no less than 25 patches into the Mac OS X 10.5.4 Leopard update that was announced yesterday.
These address a number of Ruby vulnerabilities, as reported here on DaniWeb last month by fellow blogger Davey Winder.
So that's six of the patches accounted for at any rate. Others are a little more difficult to pin down, although Apple does say that they address operating system and application performance issues.