It contains a fix for the known issue with Self Service Password Reset (SSPR) which was fixed with an interim version only available for auto upgrade.
This version introduces an internal schema change which will require you to use MSOnline PowerShell version 18.104.22.168 or higher if you use AAD Connect to manage AD FS trustrelationship with Office 365/Azure AD.
Another fix included relies to Hybrid Azure AD joined devices. The new rules contained may result of important obsolete device from Azure AD which then may reach the deletion threshold (you should/must have been configured). You will have to temporarily disable the deletion threshold for the first sync.
You can download the new version here https://go.microsoft.com/fwlink/?LinkId=615771