A neighbour saw a group of youths running away from the address on Eastfield Drive following the attack just after 5.30pm on Tuesday night.
Police said household furnishings were damaged in the incident.
Sgt Lee Carlson of Pontefract police, said: “Mischievous Night is traditionally a busy time for policing as unfortunately some groups see the night as an excuse to commit low level anti social behaviour and crime. In this particular instance, the placing of a firework through someone’s letterbox goes beyond what is normally reported to us. We have recorded a crime for arson, which is being actively investigated.”
Call police on 101 with information.