UPDATE - 05/12/2010
Executing this script is granting permission to anonymous user to collaborate - ie adding content on SharePoint sites. Be careful with it
As explained on my previous post, the SharePoint August Cumulative update is disturbing search results from anonymous SharePoint sites.
Here is an update, while Microsoft Support is still investigating:
the issue is coming from the SPWeb.AnonymousPermMask64 attribut which defines anonymous permissions.
The support engineer which is working on the case provides me a PowerShell script which change these permissions and solved the issue (at least for the moment). This script has to be executed for EACH site collection.
$siteUrl = "<include here the site collection URL>";
$site = New-Object Microsoft.SharePoint.SPSite($siteurl);
$web = $site.OpenWeb();
$web.AnonymousPermMask64 = 68719677555;
Due to a bug in the product, anonymous comments is currently disabled
Sorry about that