Yubico ‎YubiKey 5 NFC firmware 5.7 vs 5.1.2

W1zardK1ng

I was considering to change from 2fa authenticator apps to ‎YubiKey and found this ebay seller selling it for as low as $15.40 when purchased 4 or more but those devices have older 5.1.2 firmware, which have some limitations and vulnerabilities.
i can get 2 for me and 2 for my friend who dont even use authenticator apps, our threat model is very low.
I know their firmware cannot be upgraded so can someone give some opinions on this purchase decision? Is it okay to get the 5.1.2 or save up for the upcoming 5.8 which may cost around $60, not sure if it worth investing that amount.

The-Man

W1zardK1ng
there are two types of Yubikeys
Yubikey 5 series and Yubikey security key series. Both look identical, in size, shape, colour etc.
There is nothing on the physical key to say if they are series 5 or just security keys, beware...
check what each does, on the yubico website..

I buy from Yubico themselves, expensive, yes, but I get the correct key I paid for.

All my keys are the older software.
https://docs.yubico.com/hardware/yubikey/yk-tech-manual/yk5-firmware-overview.html

W1zardK1ng

The-Man The ebay seller is selling the YubiKey 5 NFC not the security key series. Just wanted to know about the security issues of having an older version of it.

The-Man

W1zardK1ng
I don't use my keys in any online instance, so I feel older version of the software suffices.

schweizer

Important difference: The old keys are level 1 only which means certified for attacks over the internet.
The 5.7 firmware keys are level 2 which means they run a certified secure element. They are designed not to be tampered when an attacker has them in their hands.