Several Pokémon have had their stats and CP changed in Pokémon GO. Alolan Diglett has had its Attack and Defense lowered while normal Kanto Dugtrio has had a Defense increase and Alolan Dugtrio has had a Defense decrease. Ninjask has also had its Attack raised. In addition, Meltan and Melmetal have had their stats altered to be more in line with how they should be when calculating their stats from the base stats in Pokémon Let’s Go Pikachu and Let’s Go Eevee.
Source: Serebii.net @SerebiiNet