TokenMismatchException in VerifyCsrfToken.php line 46: on file upload using Elfinder

I am using CKEditor and Elfinder for a WYSIWYG editor.

Ive added config.filebrowserUploadUrl = '/elfinder/ckeditor'; to config.js in /ckeditor, which adds the Upload tab. When I select an image and click Send to Server, it throws the Token Mismatch exception.