I've just added the Client-Id header to my (working) queries as described in the CMR API docs. When issuing the request from the browser, I get (full URL truncated for brevity):
XMLHttpRequest cannot load https://cmr.earthdata.nasa.gov/search/... . Request header field Client-Id is not allowed by Access-Control-Allow-Headers in preflight response.
Does the Client-Id header need to be added to the list of allowed headers (https://developer.mozilla.org/en-US/docs/Web/HTTP/Access_control_CORS), or am I doing something wrong?