Mozilla released an update to its popular Firefox Web browser that <A HREF="http://news.zdnet.com/2100-1009_22-6099254.html?tag=nl.e589">fixes a dozen vulnerabilities,</A> seven of which it deems "critical." The most serious of the flaws could be exploited by cyberattackers to commandeer a vulnerable PC, according to Mozilla. The company, which oversees Firefox development, has published security advisories for each of the flaws repaired by the Firefox update.