If you downloaded Apple's security patch listed as Security Update 2015-002, then you still aren't safe from all of the known security vulnerabilities for Apple computers. Apple's latest security update didn't do quite as much as it should have.
That's because, according to security researcher Brian Krebs, "Security Update 2015-003 was just announced, re-patching bugs known as CVE-2015-1061 and CVE-2015-1065 that were supposedly already fixed."
So the bugs that hackers may be trying to exploit that were supposedly fixed with a patch are now being pushed back until the next patch can be released. The bug affects a programming framework called IOSurface, so it won't affect most users.
Enabling automatic updates will make sure that you get the patch when it's released. Click here for a step-by-step guide on how to do just that.