Apple's updated security measures block Java 7 in OS X. Screenshot via MacRumors.
The newly discovered zero-day flaw in Java 7 is so serious that the U.S. Department of Homeland Security has warned users to disable or uninstall it.
"We are currently unaware of a practical solution to this problem," the departments' Computer Emergency Readiness Team said. "This vulnerability is being attacked in the wild, and is reported to be incorporated into exploit kits. Exploit code for this vulnerability is also available."
But Apple has already taken measures to protect OS X users by quietly disabling the Java 7 plug-in, according to MacRumors. This was accomplished by updating the OS X "Xprotect.plist" file to require users to have installed an unreleased version of Java, "1.7.0_10-b19."
Last year, Apple stopped building its own in-house Java updates, handing responsibility over to Oracle. The company also dropped Java from the default installation of OS X 10.7 Lion in 2010.
Java was a part of what was the most serious malware threat to the Mac, dubbed "Flashback." That trojan was estimated to have infected 600,000 Macs worldwide last year, before Oracle and Apple released Java patches to remove the malware.