Hey there, mod uploads should work fine at the moment. From where in the world are you trying to upload? Feel free to email the errors in your browsers network console to support@factorio.com so I can take a closer look.
The CORS error in the logs is misleading. It just pop ups because something closes the connection of the actual file upload. Also please don't upload screenshots of your network logs in this public forum, there's a chance they contain sensitive session keys for your account.