Be aware that the update in Download Center applies to Microsoft Installer (.msi)-based edition of Office 2013. It doesn't apply to the Office 2013 Click-to-Run editions such as Microsoft Office 365 Home. (How to determine?)
Improvements and fixes
Adds support for SSL 3.0, TLS 1.1, and TLS 1.2 so that documents can be securely and successfully opened from server endpoints.
Enables single sign-on (SSO) for ADAL on cloud domain-joined computers. On cloud domain-joined computer that has Modern Authentication enabled, domain accounts seem to be logged in but can't open files.
Fixes the following issues:
When you drag an attachment from an email message that's in the Rich Text format to an OneNote page, the attachment is displayed as an image on the OneNote page and you can't open it as a file.
You use Publisher 2013 to open a document that's saved in Publisher 2010.
You copy a callout between documents in Publisher 2013 and Word 2013.
In these scenarios, the arrow direction of the callout is reversed.
When you open a protected file in a Microsoft Office 2013 application, the temporary file of the protected file is created in the profile folder but not in the temp folder.
Assume that you have an Office 365 account set in Outlook 2013. When you try to open another shared mailbox, you receive the following error message or you are repeatedly prompted to enter the credentials:
Unable to expand folder.
When you try to access SharePoint files without successfully authoring Office applications, you receive repeated prompts. Or, you receive repeated and self-dismissed prompts when you use Outlook without connection.
Microsoft scanned this file for viruses by using the most current virus-detection software that was available on the date that the file was posted. The file is stored on security-enhanced servers that help prevent any unauthorized changes to it.
You may have to restart the computer after you install this update.