Flaws rated as 'highly-critical' by security firm Secunia Mozilla Corp. developers have released an updated version of their Firefox browser that fixes a number of security issues, four of them rated critical.The update was released late Thursday, and Firefox users should receive the 1.5.0.7 patches via the browser’s automatic update system over the next few days, according to Mozilla.Research firm Secunia rates the flaws as “highly critical,” saying that they can be exploited to “conduct man-in-the-middle, spoofing, and cross-site scripting attacks, and potentially compromise a user’s system,” according to this Secunia alert. In addition to the four critical patches, the software also fixes three less-critical issues and offers some stability enhancements according to the Mozilla Web site, which also includes details about the security vulnerabilities.Browser hackers have traditionally focused on Microsoft Corp.’s Internet Explorer, but as Firefox’s market share has grown it has become a more attractive target. Firefox is now used by about 13 percent of Web surfers, according to research firm OneStat.com.It has been a busy week for IT administrators looking to stay on top of security. Important security patches were also released by Microsoft Corp. and Apple Computer Inc. On Tuesday, Microsoft released its monthly set of security patches, fixing a critical bug in its Publisher product. The company also re-released two of its August patches to fix bugs in the updates.That was followed Wednesday by Apple’s fix for its QuickTime multimedia software. This update, rated as highly critical by Secunia, fixes six bugs in the product. More details on the QuickTime update can be found on this page of Apple’s Web site. SecuritySoftware Development