Earlier this month, McDonald's Japan shipped 10,000 MP3 players as prizes in a competition they organized with Coca-Cola.
The players, carrying the McDonald's "M" logo, were shipped with 10 preloaded songs.
Unfortunately, the players were also preloaded with a variant of the QQPass password-stealing trojan. We haven't seen these players ourselves, so we can't confirm how exactly you would get hit by this trojan, but some sources report you only had to plug it into your Windows PC.
More information for affected customers is available from McDonald's Japanese web site.