Hi @Allen, Dave
Thank you for posting this in Microsoft Q&A.
I understand that you are trying to upload a seed file for OAuth Hardware Tokens, but you are having trouble escaping single quotes.
In my environment I attempted to use special characters (like David.A'******@contoso.com) in UPN and observed the same behavior. My team identified this problem earlier and is currently working to fix it. It will take some time to fix the issue. In the meantime, we suggest a workaround for this issue that Try using the user object ID instead of UPN when using special characters in UPN.
I tried the workaround on my end, and it worked as expected. I used these headers to upload a seedfile in Entra.
Hope this helps. Do let us know if you any further queries.
Thanks,
Navya.
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