If you download modifications for FeralHeart, then I suggest you get a good antivirus, such as Avast or Malwarebytes, or ZoneAlarm(ZoneAlarm may get annoying, though). I use two antiviruses(Zonealarm, and Malwarebytes), and I have not gotten a virus from modifying the game so far, but I still advise caution when modifying the game.
P.S. if you use two antiviruses, the antiviruses may conflict, so stick to one antivirus of your choosing, then you'll be able to remove any virus, if a modification gives you a virus.