Can you please find and post the error messages so we know what actually happened? This hasn't been reported to us by any of our clients, so it sounds like it might be something unique to your environment.

I wish I was getting an error message but I'm not getting any in the console or logs.  That is why I tried on a fresh install but still get the same issue.  The file is successfully uploading. Below is a copy of the response:

{"uploaded": 1, "fileName": "button_1.png", "url": "/Portals/0/button_1.png"}

Hmm... Did you check the Log4NET log files too, just in case?  This video will help you find them.  :)  

https://www.youtube.com/w...-0y8o5EBYVcCY2yzhTZk

Also, do you have any security in front of the website that might be helping to protect it, such as a firewall, CDN, and/or a WAF?  They might be getting in the way.  To determine this, you may want to use the Network tab in the Web Developer Tools to inspect the request and response for any additional error messages that might be occurring.  

The following link will help you to how to inspect the requests and responses in your browser.  

https://youtu.be/rKpqmXYUWaQ?t=25

Thanks for the suggestions.  Those logs did not show anything.  The fresh 9.11.2 I installed runs locally so that should rule out the WAF, SSL, or anything like that.

Okay, well then it's a fixed issue.  That's great to know.  You should be able to upgrade to resolve this.  I'd recommend trying this first on a test/staging version of the website in the same environment first.  :) 

Not a fixed issue.  It is still an issue.  I can reproduce the issue on three 9.11.2 sites including a brand new fresh install.  I know CKEditor is a newer version and there were some additional plugins like easy-image added from 9.10.2 so perhaps that response type got changed or something else and it is not working for uploads from dialogs correctly.

There's a known issue with EasyImage, but when you also have an isuse with other images, please log that issue on Github.

Here's a direct link for you to report bugs like this:  

https://github.com/dnnsof...rm/issues/new/choose

Just to follow up my issue was resolved by having the response for the upload dialogs changed back to

this.Response.Write("<script type=\"text/javascript\">");
this.Response.Write(this.GetJsUploadCode(fileName, MapUrl(uploadPhysicalPath)));
this.Response.Write("</script>"); 

Instead of just the JSON response for everything that was added in 9.11.1.  You still want to keep the JSON for dragging and dropping which adds the responseType=json