You may have an old copy of Microsoft Office lying around that you suddenly decide to install on your new Windows 10 computer and wonder if there will be any issues.
Will if support has ended there can be with security being the big issue as opening Office files with an old copy of Office can leave you vulnerable to virus / malware issues.
Will your antivirus be able to save you in this case ?
No , as most run as an administrator you are actually giving permission for the virus / malware to run.
There is also the compatibility issues when trying to open new versions of files.