The first thing you need to consider is that you have to download the program from a trusted site because if you do not do that, it might create a problem for you.
It may delete the files or corrupt the files in your computer; that is why you need to download them from a trusted source. Otherwise, you may have to face some big problem that you may not want to.
Another risk that you can get from the mod skin pro is that if you use different skin in one day, you will be able to lock out the account. It means you will not be able to use it further and left with no option but to quit.
You may get a ban, or your account will be ban from the game if you will not play it in a good way. You also need to choose a reliable platform from where you can download it.
If you want to know more at LoL mod skin Pro, read this article.