Would be pretty hard to do.
For one, new products go through the world most awful validation process you’d ever witness…
That would probably catch new items/new developers.
For seconds, even if you could potentially plug a bad file intentionally into your product after validation, you’d screw your marketplace earnings for no real reason…
Also, all the packs usually include parsed .uasset files, not direct .fbx.
The fbx gets created when you export, which is why it’s generally safe to begin with.
Anyway, by not making silly decisions like downloading from unknown sources you already cut the risk of potentially having to format your hard drive… and on windows, formatting once every 3 months is probably a very good idea…