Hi,
My suggestion is to limit the file types that will be uploaded.
During you upload submit action, you can validate the file type of the file.
You can use this reference for MIME Types - The Complete List.
One of the files that needs to blocked are the .exe file which usually treated as malicious files.
Also, you could add a validation for the file size (usually, maximum of 5mb file will do)
Hope this helps!
Regards,
Marco