Apple has released a security update with a total of 13 fixes for vulnerabilities in Mac OS X Panther and Tiger.

The update is available for download through the company's Web site, or through Apple's automatic update service. Panther is OS X version 10.3, and Tiger is 10.4.

As company policy, Apple does not rate the seriousness of its vulnerabilities, and releases updates on an as-needed basis, a spokesman said. The most recent update, released Thursday, is the fifth of the year.

The patches cover the desktop and server versions of the operating system. The flaws fixed range from the benign, such as a hacker inserting code that would result in the sudden termination of an application; to the more critical, such as making a computer vulnerable to password theft or a denial of service attack.

Early this month, Apple fixed a highly critical vulnerability in QuickTime by releasing a new version of the media player. The update was for the Mac OS X and Windows, and patched a hole that could open up the millions of people who use an iPod to attacks on their desktops and laptops.