title: Access-Control-Allow-Origin header contains the invalid value
body: <p>I have created html page with <code>form</code> <code>submit</code>. On submit i am calling ajax <code>post</code> request.
  But throws a error </p>
  
  <blockquote>
    <p>Failed to load <a href="http://radius.a3techlabs.com/app/custom/verifyAccessOTP" rel="nofollow noreferrer">http://radius.a3techlabs.com/app/custom/verifyAccessOTP</a>: Response to preflight request doesn't pass access control check: The 'Access-Control-Allow-Origin' header contains the invalid value ''. Origin 'null' is therefore not allowed access.</p>
  </blockquote>
  
  <pre><code>$.ajax({
        url: 'http://radius.a3techlabs.com/app/custom/verifyAccessOTP',
        dataType: 'json',
        type:'post',
        headers: {
            "charset":"UTF-8",
            "accept": "application/json",
            "Access-Control-Allow-Origin":"*",
            "Access-Control-Allow-Credentials":"true",
          },
        data:value,
        success: function(data) {
          console.log(data);   
          alert(data.message);
        }.bind(this),
        error: function(xhr, status, err) {}.bind(this)
      });
  </code></pre>