Doesn't work on Firefox 59 on a Mac

This addon doesn’t seem to work on Firefox 59 on MacOS. Attached you can find a screenshot with the console output on Firefox and on Chrome. You can see in the screenshot that the request is blocked on firefox and works on Chrome.

I disabled Cors on Chrome running it with this command:

"/Applications/Google Chrome.app/Contents/MacOS/Google Chrome"  --disable-web-security --user-data-dir=/Users/mac/chromeprof  --allow-running-insecure-content --allow-file-access-from-files

I modified the file cors-everywhere-html this way:

var xhr = new XMLHttpRequest();
            xhr.open("get", "http://google.com", true);
            xhr.withCredentials = true;
            xhr.onreadystatechange = function(r) {
                document.getElementById("response").innerHTML +=
                    "<hr />readyState: "+r.target.readyState+
                    "<br />status: "+r.target.status;
                    
                    if (this.readyState == 4 && this.status == 200) {
                        console.log(this.responseText);
                        console.log(this)
                        console.log(r)
                      }
            }
            xhr.send();

[Medtrack]

Ok. I found the issue!!! My fault. Thank you very much for your job! Sorry for the inconvenience. The problem was that I have the Duckduckgo Privacy Essentials addon and it looks like that plugin blocks this one. I can disable that plugin and it works.

[Medtrack]

It keeps failing on my computer. The button is in the top bar and enabled. There’s a message in the console in Spanish. It says this: "Request from another origin blocked: the same origin policy disallows reading the remote resource in … ".

It’s version 17.7.16.1852 from firefox addon page. If I have time, I will try to debug later.