Separate from their larger updates, Apple has released a patch to address two flaws in QuickTime, both of which could lead to arbitrary code execution. The vulnerabilities, both of which stem from QuickTime's Java implementation, could expose a system if someone were to visit a maliciously crafted website. The majority of security updates do seem to be centered around that, which makes perfect sense. Browsing the web is one of the few aspects that just about every Internet-connected desktop has in common. Being that QuickTime is a fairly popular media player, it makes sense that it would become a more popular target.
Apple has been in the news quite a bit this year with security updates, partially due to the increased attention on OS X and the increasing (albeit slowly) marketshare of the Mac. You can read the advisory surrounding these two flaws at Apple's site.