Hi @Sasuke_Chang,
I moved your comments to a separate post so it can be addressed here. I wanted to point out this post here: Limiting uploaded file types - #5 by asmecher, which discusses the allowed uploads plugin that you might want to look into to help with this issue. Also, it might be worth having a look at our administrator’s guide recommendations on configuration: https://docs.pkp.sfu.ca/admin-guide/3.3/en/configure - this may help address some of the issues you’re facing, but if you have additional questions, please let us know.
-Roger
PKP Team