There are certain file types that users cannot upload

Assignments Pro gets its list of allowed file types from WordPress. So if it’s not allowed by WordPress, then it won’t be allowed by anyone uploading a file.

WordPress has a strict list of allowed file types that it lets you upload, because certain file types could potentially be dangerous and open your system up to risks.

If there are certain file types that you want WordPress and Assignments Pro to allow, then you can alter these using a developer hook:

upload_mimes