I was thinking about that, too; anyone can upload anything, and anything can be malware.
However, if you have Forge installed on your server, there is a "Mods" tab on the left, where you can select and install any mods that Aternos supports. I was thinking that if this "Mods" tab could be incorporated into any server with a modpack installed, you could have a modpack installed on your server(from those which Aternos supports) and maybe an extra few that the modpack left out viz the "Mods" tab, if it is incorporated. 'That way, nothing is dragged from your computer, rather, all the files would be Aternos's.