I am using ckeditor 4.11 and the problem is that you do not want to upload an image, it sends me a message that says "Incorrect server response".
This is what I have code:
<form action="" method="post"> <textarea name="editor" id="editor"> </textarea> <br> <input type="button" value="Subir" name="boton" onClick="agregar();"> <script> var editor = CKEDITOR.replace('editor'); </script> </form>
In the config.js file of the ckeditor:
config.filebrowserUploadUrl = 'upload.php';
I upload the file upload.php to the same location where I have the index.php file.
In another older version that I have of ckeditor I have no problems but the issue is that this version is not compatible with the video plugin and that's why I had to change the version.