LOS ANGELES, June 13 (Xinhua) -- Microsoft on Tuesday released its largest clutch of security patches for 21 flaws in the Windows operating system, the Internet Explorer web browser, and the Office productivity software.

      Sending out a dozen security bulletins on Tuesday as part of its regular monthly patch cycle, the software giant said all but two of these leaks could let an intruder run malicious code on a compromised computer.

    The company labeled eight of the bulletins covering Windows and Office as "critical," which is Microsoft's highest risk rating.

    Four of the critical updates deal with security holes that could allow remote code execution in all versions of Windows, while one is a cumulative update for the Internet Explorer.

    Another patch deals with a problem with the Windows Media Player. Two updates affecting Office were also given the highest risk rating. This is Microsoft's largest clutch of patches to date, security experts said.

    "There has never been a Microsoft security update to address 21 issues and never one with 19 potential remote execution flaws," Amol Sarwate, manager of the Vulnerability Management Lab at computer flaw management firm Qualys, told the CNET news.

    The most important bulletin is a fix for routing and remote access vulnerabilities in Windows. The routing and remote access are deemed critical for systems running Windows 2000, and "important" -- the second risk ranking -- for Windows XP, and for Windows Server 2003.

    IT administrators must be busy deploying the bundle of patches across their network over the next days and weeks, experts forecast.

    "There are a couple different vulnerabilities. Some are Internet Explorer browser problems, some affect the Windows Media Player, ART imaging and JScript," said Chris Andrew, vice president of security technologies at Patch Link.

    "IT managers will probably have to patch every single desktop,"he added. Enditem