Scammers intentionally abuse custom-offer-messages to lie, from saying fake prices to "Hey you won -thing-! Accept this trade to claim your prize! Or the thing I said you'll get, but only after you accept this trade!", so please beware. All items of that trade are in that trade. There's also account hijacking: Someone could've stolen your friend's account and is now trying to steal yours by impersonating them! You shouldn't have to do anything weird someone tells you to do. Thieves use fake, official-looking media to trick you into believing they're Valve employees. Hijackers say you can't recover your account because they changed its information. They're lying again, please disbelieve them and talk to Steam Support. In all cases, please let Steam handle disputes for you and don't click links that ask you input additional data or take you outside Steam. Steam isn't everywhere, if someone gets you to talk to them where Steam can't interfere, they'll steal from you using their creativity/smarts for evil x.x