It comes down to whether you can demonstrate this flaw. If you have a way to show it actually working then credentials shouldn't matter.

If your attempts at disclosure are being ignored then check:

• am I presenting this in a way that makes me seem like a deranged crazy person?
• Am I a deranged crazy person?

Try to resolve those. If the company you're trying to contact is still send your emails to the spam bin, maybe try contacting other people who have done disclosure on issues like this before. If you can convince them then they can use their own credibility to advance the issue.

If that doesn't work then I guess check the "deranged crazy person" things one more time and move on to disclosing it publicly yourself.