I got one from greenhouse today saying that a company I've never heard of is no longer considering my application. Is this some kind of H1B fraud? Is it a recruiter just submitting my resume? Something else?
Hmm, is it definitely your application with your personal details? I've had a few instances where someone with the same name (and a very similar email address) accidentally used my email address instead of theirs when signing up for things online. So maybe they used your email by mistake or something, especially if you're using something like Gmail for it.
If it's definitely based on your details, then yeah, impersonation seems likely.
I have read before that some people apply for remote jobs using other people's credentials that they have collected from publicly available sources like home-pages, etc.