It was just announced over on the SharePoint Team blog:
    http://blogs.msdn.com/sharepoint/archive/2008/07/15/announcing-availability-of-infrastructure-updates.aspx

This is an important update and is publically downloadable using the links on the SharePoint team's blog entry.  We are recommending that all customers apply these updates.  Please schedule a time to test them in your test enviornments, and also time for production upgrades.  As with any upgrade, you will need go through an upgrade on all of your content.  So the more content you have, the longer it will take.  We do recommend that if you have MOSS that you apply both the WSS and MOSS packages and not just WSS or MOSS.  The MOSS package (build 6322.5000) contains both the Global and Localized patches for MOSS (you should see 42 MSPs).  The WSS package (build 6320.5000) contains only the Global patch (there is 1 MSP).  It is recommended that you look to see if you need the latest WSS Localized patches (6309.5000) as well--which at the time of writing this post is:  http://support.microsoft.com/kb/953484