An update has been released for Outlook 2013 and can be downloaded and installed manually, but is also being offered via Microsoft Update.
Update KB2817629 for Outlook 2013
This is a non-security update which has been released without a change log. However, it will fix the issue which got introduced in the July update where Outlook 2013 crashed when you try to select or open an encrypted message.
If you have Microsoft Update configured to also update other Microsoft applications, then this update will also also be offered via Microsoft Update or has already been updated automatically for you.