When an object changes controller it does not untap unless the effect that causes this change in control specifically says to untap it.

There are plenty of ways to 'steal' permanents in Magic. When a permanent does change controllers it is the same object that was previously in play. If it is a creature it will not be able to attack the turn it is 'stolen' unless it has haste or the effects that causes it to change controllers gives it haste. However sometimes even if the creature has haste that won't work. As this permanent is the same object it will still be tapped or untapped. As with granting haste, some change of control

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