Apple has patched a "theoretical vulnerability" in the Help Viewer application, part of the Mac OS X operating system.
The company is urging all OS X users to download the patch for the flaw, which it said "could have been exposed when browsing the web".
"Apple takes security very seriously and works quickly to address potential threats as we learn of them, in this case before there was any actual risk to our customers," said Philip Schiller, Apple's senior vice president of worldwide product marketing, in a statement.
"While no operating system can be completely immune from all security issues, Mac OS X's Unix-based architecture has so far turned out to be much better than most."
Schiller added that, to maintain maximum system security, Mac OS X users should keep their system current by installing this and all Mac OS X software updates.
The update is available automatically to all users through Apple's free Software Update service or by visiting the company's download website here.
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