authentication – What are the security risks to NFC based YubiKeys?

What are the risks of using NFC on a YubiKey versus just a hard connector?

I imagine it would be possible to sniff some data off of these security keys? How real is the risk of sniffing and what could an attacker gain from such an attack (only ephemeral data I am hoping)?

My main concern is that an attacker could basically get access to a long-lasting way to perform authentication.