CORS预检OPTIONS请求返回错误，但仍在发送POST

Question

I'm making a cross-domain request to an asmx service from my site using jQuery ajax as follows:

$j.ajax({
  url: svcURL,
  type: "POST",
  data: xml,
  contentType: "text/xml",
  dataType: "text",
  success: function(d) {
    alert(d);
  },
  error: function(a, b, c) {
    alert("error");
  }
});

This POST request is preceded by a preflight OPTIONS request which the service is not configured to deal with currently, so it returns with either a 500 (Internal Server Error) or a 405 (Method Not Allowed) .

After receiving this error, I would expect the browser to then ignore the POST request and return an error, however:

In Chrome & IE the POST request is still sent (which the service is correctly configured to deal with) and a response is received.

In Firefox the POST just returns an error.

Could someone explain the reason why this works in Chrome? I would have expected it to behave how Firefox does.

Thanks for any help in advance.

Answer 1

There is a bug in Chrome and WebKit that sends the subsequent request even if the OPTIONS request fails.

Firefox follows the CORS spec correctly and cancels the request once the preflight fails.