KB2889866 released just yesterday, but it has already been pulled by Microsoft.
The update was designed to fix problems with OneDrive for Business, specifically for syncing new libraries in a couple instances. KB2889866 is not a security update, just a feature fix.
Microsoft has just pulled the update from the catalog and issued this statement:
We are investigating an issue that is affecting the September 2014 update for Microsoft OneDrive for Business. Therefore, we have removed the update from availability for now. We apologize for any inconvenience that this might cause.
Microsoft has not supplied what the problem actually is or if keeping it installed will cause issues, just that they are investigating.
More as this develops…