Microsoft has released a fixed version of an earlier update to Outlook 2013 that had been pulled from distribution.
The update was released originally as part of September's Patch Tuesday updates. But within a few days Microsoft acknowledged problems caused by the update and pulled it from their distribution systems. Users reported that, after applying the update, the Outlook folder pane disappeared. Removing the update reversed the problem.
The update affects only Outlook 2013 and is not a security update. According to Microsoft, it contains "stability and performance improvements."
This was not the only problem with this month's Patch Tuesday updates, and it was in fact part of a longer pattern of code quality problems in Microsoft updates.