Ajax call bug with Chrome new version 73.0.3683.75?

My code was working fine before the Chrome update.

I make an ajax call to my server. My server receives the call, returns JSON to the client, but the answer is always empty. When I look in Fiddler I get an answer from the server.

I try with JQuery, and I also try with an xmlhttp call. Always the same result

Did new CORS policy rules apply...?

There is my xmlHTTP call

 var xmlhttp = new XMLHttpRequest();   // new HttpRequest instance 
      var theUrl = "URL";
      xmlhttp.open("POST", theUrl);
      xmlhttp.setRequestHeader("Content-Type", "application/json;charset=UTF-8");
      xmlhttp.send('{ "args" :{ "Obj":"my obj"}}');
      xmlhttp.onreadystatechange = function(state,xhh,aaa){
        if (xmlhttp.readyState == XMLHttpRequest.DONE) {
          alert(xmlhttp.responseText);
        }
      }

The ajax call is similar

$.ajax({
        url: "URL",
        data: '{ "args" :{ "Obj":"my obj"}}',
        dataType: "json",
        contentType: "application/json; charset=utf-8",
        type: "POST",
        async: false,       
        error: function (xhr, ajaxOptions, thrownError) {
          if (that.Fail != null) {
            that.Fail();
          }
        },
        success : function(data){

           alert(data);

        }
      })

I had the same problem after upgrade to Chrome 73. Thanks to @wOxxOm

This is the workaround until now: