Unfortunately, it looks like they squinted and left him. I have the same problem.
According to this , there is no way to set the Content-Type header, and I myself have not found a way. You will see that they actually made this WORSE a later bug fix. Since XDomainRequest is deprecated in IE10 for the correct XMLHttpRequest object using CORS, I doubt there will ever be a fix.
If you have ever found a way to solve a problem, bring it back and let the world understand. This prevents me from using Amazon S3 POST to upload avatars.
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