Authorization for image upload

i implemented ckfinder and ckeditor in my cakephp 3 and the problem is when i browse and select an image from my computer to upload it an error happens and says “error sending the file”.
i think the problem is that cakephp does not allow it. maybe i need to authorise it but it is not an action in a controller to authorise. what can i do?

have you set “filebrowserUploadUrl” path in ckeditor config?

U use trial ckfinder??