Microsoft has pulled one of the three critical patchesfrom yesterdays Patch Tuesday, MS13-061, from further distribution. Itseems that applying this update to Exchange Server 2013 results in theContent Index for mailbox databases showing as Failed and the MicrosoftExchange Search Host Controller service getting renamed. This is notgood. If you have already installed MS13-061 Microsoft has published KB2879739 to show youhow to fix it.
If you already installed MS13-061 on Exchange 2007 and or 2010 it lookslike you should be good to go as the issue does not seem to occur withthose versions.
Seeing as this is a critical update and that could result in remote codeexecution and that the patch has already been made available, even if fora short time, you have to assume that the bad guys are actively working onexploit code for this issue. So what should you do? Microsoft thankfullyincluded a workaround in the original Security Bulletin for this problem, which could help mitigate things untilMicrosoft can reissue the patch. It involves issuing some PowerShellcommands on the server and are detailed in the Security Bulletin.