Apple has at last fixed a critical vulnerability with its Mac OS X operating system. The flaw opened a mechanism for hackers to execute harmful code on vulnerable systems by tricking users into visiting maliciously-constructed websites.

Apple initially said that a fix for a "Help" URI handler vulnerability released last month solved the problem. But security researchers were able to show that flaw was still present, even on fully patched systems. An update released yesterday finally addressed the "extremely critical" vulnerability, according to security firm Secunia, which has monitored the issue closely over the last three weeks. This assessment is supported by Mac enthusiast sites, such as Unsanity.

Thee patches are cumulative fixes designed to improve the security of Mac OS X systems. Each fixes a handful of security problems.

Despite the apparent seriousness of the flaw, there's little evidence that it was actively exploited to break into vulnerable systems. ®

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