The update fixes a pair of flaws that could be used to create a virus that spreads through a Web link sent via e-mail messages. An attacker also would have to create a Web site with special programming to exploit the vulnerability.
The issue was made public last week, although the person who discovered the problem claims to have notified Apple in February.
Security information service Secunia rated the issue "extremely critical," because online discussions have pointed out many different ways to exploit the flaws.
Apple took the unusual step of issuing a press release to tout its security update, but a representative refused to answer all questions regarding the issue, including why it has taken since February to get a patch for the software.
"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," Philip Schiller, Apple's senior vice president of worldwide marketing, said in the press release.
The Mac has generally had a reputation for having fewer security issues--and less serious ones than Windows-based machines. However, Apple has recently been criticized for not adequately disclosing the nature of flaws in OS X and for its lack of response to security industry concerns.
Apple encouraged all Mac owners to install all Mac OS X updates on their machines to best protect their systems.
Macintosh - Security by obscurity. I'm sure it will keep the impression of security, as long as it retains such a small market share...