Is Misleading Signpost legal in Standard, Modern, and Commander?

Misleading Signpost is legal in: Legacy, Vintage, Commander.

Misleading Signpost

Q: What type of card is Misleading Signpost?

Misleading Signpost is an Artifact. Its oracle text reads: "Flash When this artifact enters during the declare attackers step, you may reselect which player or permanent target attacking creature is attacking. (It can't attack its controller or their permanents.) {T}: Add {U}."

Artifact

Flash

When this artifact enters during the declare attackers step, you may reselect which player or permanent target attacking creature is attacking. (It can't attack its controller or their permanents.)

: Add .