Explode does make an attack. Fireshaper Ring does not influence it.
It's not a melee or ranged attack, and the mage isn't directly making the attack anyway, Explode is. I could be remembering the wording on Explode wrong in terms of whether the mage is considered to be making the attack, but I'm sure it's not a melee or ranged attack, so it doesn't benefit from Fireshaper Ring regardless.