Steam Support will never ask you for your full 16-digit credit card number, expiration date, or the security code for your card. In some cases, to verify proof of ownership, we may ask you to confirm the first or last digits of your credit card. For your security, please never provide your entire credit card number, expiration date, security code, or password. In the case that this information is provided, Steam support will edit your ticket to remove any sensitive data.