The latest version of Windows 10 Mobile is Version 1709 which was released in October 2017. Microsoft won’t support this version of Windows 10 Mobile anymore starting December 10.
With end of support for Windows 10 Mobile version 1709 all Windows 10 Mobile devices have moved out of any security update support from Microsoft. This end of support date is applicable to the Windows 10 Mobile enterprise also.
As mentioned on the official page,
Windows 10 Mobile, version 1709 (released October 2017) is the last release of Windows 10 Mobile and Microsoft will end support on December 10, 2019. The end of support date applies to all Windows 10 Mobile products, including Windows 10 Mobile and Windows 10 Mobile Enterprise.
Windows 10 Mobile users will no longer be eligible to receive new security updates, non-security hotfixes, free assisted support options or online technical content updates from Microsoft for free.
All other Windows 10 Mobile versions have already ceased to receive support from Microsoft with their lifecycles coming to an end.
