To increase the security of your Automad installation, it is only allowed to upload files which are on the whitelist of allowed file types. All common media file types are already on that list by default. In case you want to extend the whitelist, you can edit the
config/config.json as mentioned before.
"AM_ALLOWED_FILE_TYPES": "dmg, iso, rar, ... mpeg, css, js, md, pdf",