Yes, it does affect your attack stat.
>Foul Play inflicts damage. It uses the target's Attack stat to calculate damage, as opposed to the user's Attack stat. The target's Attack stat modifier is incorporated into damage calculation. With the exception of the Attack stat and Attack stat modifier, all other factors affecting damage calculation, including the item, Ability, type, and status ailment of the user of Foul Play, are incorporated as normal.
Hope I helped.