The Exchange Team released the December updates for Exchange Server 2013 and 2016. Apart from the usual set of fixes, these Cumulative Updates also have the following enhancements:

• Like announced earlier, these quartely updates introduce support for .NET Framework 4.7.1. Be advised that .NET Framework 4.7.1 will be required for the quarterly updates to be released in June 2018.
• Upgrading an existing Exchange deployment with these Cumulative Updates will preserve TLS cryptography settings.
• Support for Hybrid Modern Authentication (Info).

Exchange 2016 CU8 fixes:

• 4056329 Can’t access EWS from Outlook/OWA add-ins via makeEwsRequestAsync in Exchange Server 2016 and Exchange Server 2013
• 4054516 “Your request can’t” error when accessing an archive mailbox via OWA in Exchange Server 2016
• 4055953 The recipient scope setting doesn’t work for sibling domains in Exchange Server 2016
• 4055435 No MAPI network interface is found after you install Exchange Server 2016 CU7
• 4056609 Event ID 4999 and mailbox transport delivery service does not start after you install Exchange Server 2016 CU7
• 4045655 Description of the security update for Microsoft Exchange: December 12, 2017
• 4057248 Many Watson reports for StoragePermanentException in Exchange Server 2016

Exchange 2010
In addition the Cumulative Updates, Exchange Server 2010 SP3 also received an important update, which fixes the issue described in KB4054456. You can download Rollup 19 here, which will raise the version number to 14.3.382.0. The related KB article is KB4035162.

• Exchange 2016 CU7 and later requires Forest Functionality Level 2008R2 or later.
• Exchange 2016 CU8 and Exchange 2013 CU18 do not contain schema changes compared to their previous Cumulative Update. However, they may introduce RBAC changes in your environment. Use setup /PrepareSchema to manually update the schema, or use /PrepareAD to apply RBAC changes, before deploying or updating Exchange servers. To see if you need to update the schema compared to your version or verify the update has been performed, consult the Exchange schema overview.
• When upgrading your Exchange 2013 or 2016 installation, don’t forget to put the server in maintenance mode when required. Regardless, setup will put the server in server-wide offline mode post-analysis, before making actual changes.
• Using Windows Management Framework (WMF)/PowerShell version 5 or later on anything earlier than Windows Server 2016 is not supported. Don’t install WMF5 on your Exchange servers running on Windows Server 2012 R2 or earlier.
• When using Exchange hybrid deployments or Exchange Online Archiving (EOA), you are required to stay at most one version behind (n-1).
• If you want to speed up the update process for systems without internet access, you can follow the procedure described here to disable publisher’s certificate revocation checking.
• Cumulative Updates can be installed directly, i.e. no need to install RTM prior to installing Cumulative Updates.
• Once installed, you can’t uninstall a Cumulative Update nor any of the installed Exchange server roles.
• The order in which you upgrade servers with Cumulative Updates is irrelevant.

Caution: As for any update, I recommend to thoroughly test updates in a test environment prior to implementing them in production. When you lack such facilities, hold out a few days and monitor the comments on the original publication or forums for any issues.