If you're using Mac OS X, fire up the App Store: Apple has issued a series of security patches. Details can be found in an article on ZDNet here:
Tech-security journalist Larry Seltzer writes:
"In addition to fixing a high-priority bug in SSL/TLS and shipping numerous feature tweaks and fixes, Apple released a large number of security fixes today to OS X, Safari and QuickTime for Windows.
There were 33 vulnerabilities patched in OS X, four in Safari and 10 in QuickTime for Windows."
As of this writing there is little information online, and almost nothing on Apple's own site. But Seltzer's article details many previous patch-releases from Apple.
Given the seriousness of the recent vulnerabilities, I urge Apple to be more proactive in informing its users on these matters. Meanwhile, whether using 10.7, 10.8 or 10.9, patch your OS X operating system now! Note that the system will restart after you download the patches, so save your work and allow a bit of time for the process.