Redeem Steam key to account with Steam OpenID like Humble Bundle

Humble Bundle has started requiring the user to sign in through Steam's OpenID authentication where it then redeems the Steam key on the user's account. I was unable to find any documentation on this

Account got Hijacked - Please DON'T make my mistake!

Steam (service) - Wikipedia

Steam (service) - Wikipedia

Free Game Redemption Instructions – Humble Bundle

How to Link Your Steam Account – Humble Bundle

Steam Key Redemption – Humble Bundle

Humble Bundle] Humble intergalactic Bundle: PWYW for Space Hulk

G2A sold $450k worth of our game keys : r/Games

How to Buy a Humble Bundle and Redeem It on Steam

How to Redeem a Gifted Bundle or Game – Humble Bundle

Anyway to find Steam keys that are revealed but not redeemed? : r

G2A sold $450k worth of our game keys : r/Games

Steam (service) - Wikipedia