For several years we have successfully been uploading videos via the YouTube API using some custom JavaScript code. The code was based on some samples provided by Google (cors_upload.js). It's not something we use a lot, just every couple of weeks.
Things were working fine a couple weeks ago, but it has come to my attention that things recently stopped working. We login fine, we obtain the channel info fine. But when we start the upload (which happens via XHR …