原因在于iis不支持.json擴展名，官方教程地址https://ckeditor.com/docs/ckfinder/ckfinder3-php/quickstart.html#quickstart_troubleshooting_json

You will thus need to?add JSON as a new MIME type?in your IIS configuration.

Set the following options in the?Add MIME Type?dialog:

• File name extension:?.json.
• MIME type:?application/json.