As expected, today Microsoft released a security bulletin for Internet Explorer outside of its normal monthly patch cycle. This bulletin (MS10-018) is a cumulative security update for all supported versions of Internet Explorer. It fixes the vulnerability I wrote about earlier this month, but it also addresses nine other vulnerabilities. The update has a Critical severity rating for all versions of Internet Explorer on all supported Windows clients (2000, XP, Vista, 7). It is rated Important or Moderate for server versions of Windows.
(The monthly Security Bulletin Summary for March has been updated to include this release.)
At least one of these vulnerabilities is currently being exploited via the Internet, so I recommend installing this update as soon as you can. It is available via Windows Update, or can be downloaded from the links in the bulletin.