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Apple apparently also retired Mac OS X 10.4, aka Tiger, from security support; none of the patches affect that operating system, which debuted in April 2005. Apple traditionally stops providing security updates for its oldest still-supported OS several months after the release of a new edition.

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Today's security update was the sixth from Apple this year, and the second that included patches for Snow Leopard , launched in late August.

"Seems a little large, but really, it's par for the course for Apple," said Andrew Storms, director of security operations at nCircle Network Security, referring to the number of individual bugs quashed in today's 2009-006 update. In May, Apple patched a record 67 vulnerabilities ; it addressed 55 in February, 33 in September, and 19 in two separate August updates.

"Thank goodness Apple didn't release it tomorrow," Storms said. Microsoft, which unlike Apple sets a regular schedule for its security updates, is slated to deliver six updates Tuesday that will patch 15 vulnerabilities.

More than half of the vulnerabilities patched today, 32 out of the 58, were accompanied by the phrase "may lead to arbitrary code execution," which is Apple's way of saying that a flaw was critical and could be used by attackers to hijack a Mac. Apple does not assign ratings or severity scores to the bugs it patches, unlike other major software makers, such as Microsoft and Oracle.

Apple plugged holes in 37 different components of Mac OS X, ranging from AFP Client and the open-source Apache Web server software to CoreGraphics, the Help Viewer and the Spotlight desktop search engine.

Storms said several were worth particular attention, including the four that patched critical vulnerabilities in the version of QuickTime originally packaged with Mac OS X 10.6, aka Snow Leopard .

"Those were the vulnerabilities Apple patched in QuickTime 7.6.4," said Storms, noting that Apple issued a separate QuickTime update for Mac OS X 10.4 and 10.5, Tiger and Leopard, respectively, on Sept. 9, just 12 days after debuting Snow Leopard.

Apple delivered Snow Leopard's first security update on Sept. 10 to fix nine flaws in Adobe's Flash Player that it had plugged in late July, but was unable to squeeze into Snow Leopard before its launch.