Office 2016 has received numerous security updates (e.g., for remote code execution in Excel and Outlook). Files from 2016-era indexes will lack these patches, leaving your work machine vulnerable to exploits like CVE-2017-11882 (the notorious Equation Editor vulnerability).
If you need Office 2016 64-bit for legitimate use, here are the safe sources: index of ms office 2016 64 bit work
