Unauthorized downloads are a common vector for ransomware and spyware.

: Unauthorized or "patched" versions may contain modified code that produces incorrect mathematical results, rendering research data invalid.

Cons:

Gaussian 16W is a sophisticated computational chemistry software

But perhaps the most painful irony is this: We search for “Gaussian 16w download upd” because the software itself is a black box. Updates rarely come with transparent changelogs. You download, install, and pray your old input files still run.