Is Urza's Dark Cannonball legal in Standard, Modern, and Commander?

Urza's Dark Cannonball is legal in: Commander.

Urza's Dark Cannonball

Q: What type of card is Urza's Dark Cannonball?

Urza's Dark Cannonball is a Stickers. Its oracle text reads: "{TK}{TK} — Exalted, exalted (Whenever a creature you control attacks alone, it gets +1/+1 until end of turn for each instance of exalted among permanents you control.) {TK}{TK}{TK} — Shadow (This creature can block or be blocked only by creatures with shadow.) {TK}{TK} — 1/5 {TK}{TK}{TK}{TK} — 7/4"

Stickers

— Exalted, exalted (Whenever a creature you control attacks alone, it gets +1/+1 until end of turn for each instance of exalted among permanents you control.)