The games that I have downloaded from itch have not been viruses. But, I have seen games that I'm 99% sure are. If it's a reupload of a legit game, don't download it. I saw someone who had several projects of games like Pokemon Snap and 007: Golden Eye, which were all viruses because it was definitely not the actual developer. A potential way to determine if it's a virus is if the project page has very little work put into it but the game looks super high quality. I just try to be careful, I still download games. But, if you do have another thing like you found of two zipped folders inside each other, delete the file, empty the trash, and report the project page. Also, never click on links comments that say things like "New version here ..." It's to bad that there are viruses on itch, though. There are some great games on here, but you've just got to be careful.