Microsoft released Update Rollup 1 (UR1) for on-premises and partner-hosted Microsoft Dynamics CRM 2013, resolving 32 issues. The build number is (6.0.0001.0061) or (06.00.0001.0061), depending where you read it.
UR1 is available now for manual download.
UR1 will be available through Windows Update in January 2014.
Links
Microsoft Support knowledge base article 2891271: http://support.microsoft.com/kb/2891271
Microsoft Download Center: http://www.microsoft.com/en-us/download/details.aspx?id=41546
Microsoft Developer Network (MSDN) blog article: http://blogs.msdn.com/b/crminthefield/archive/2013/12/17/podcast-and-overview-microsoft-dynamics-crm-2013-update-rollup-1.aspx