Is Mass Diminish legal in Standard, Modern, and Commander?

Mass Diminish is legal in: Legacy, Vintage, Commander.

What type of card is Mass Diminish?

Mass Diminish is a Sorcery. Its oracle text reads: "Until your next turn, creatures target player controls have base power and toughness 1/1. Flashback {3}{U} (You may cast this card from your graveyard for its flashback cost. Then exile it.) *Transformed from brute to cute.*"