moz-chunked-arraybuffer response type for the
XMLHttpRequest.responseType property, deprecated since Firefox 58, has been removed with Firefox 68. You can instead use
fetch() in combination with the Streams API which is available since Firefox 65. See Using readable streams on MDN for details.
Update: The initial version of this note was mentioning the
arraybuffer type as an alternative but it was wrong. We have corrected note according to the feedback.