Serial Hack For Mount&blade I Sold My Macbook On Ebay But They Said They Want My Serial # Off The Box. Would It Be Bad If I Sent It?

I sold my macbook on ebay but they said they want my serial # off the box. would it be bad if i sent it? - serial hack for mount&blade

I sold my MacBook on eBay, but they said they wanted my serial number. Shall I love them or they can hack into my computer, or a potential scam, or is it just to be somebody up?