Can a player attack with a creature the same turn that creature's controller changes due to an opponent's effect?

When a permanent's control changes, it is treated similarly to a newly arrived permanent for the purpose of the 'summoning sickness' rule. Under CR 302.6, a creature can only attack (or use tap-symbol abilities) if it has been under its controller's control continuously since the beginning of that player's most recent turn. A mid-turn control change resets this clock for the new controller.

So if an opponent uses an effect like Act of Treason or Blatant Thievery to take control of your creature during their turn, that creature is now under their control but has not been since the beginning of their turn. Unless the creature has haste (CR 702.10), it cannot attack that same turn.

Haste explicitly overrides the summoning sickness rule (CR 702.10a), allowing a creature to attack and use tap-symbol abilities regardless of how recently it came under the current controller's control. So if the stolen creature already has haste, or gains it after the control change, it may attack immediately.

Concrete example: Your opponent casts Act of Treason on your Grizzly Bears (a vanilla 2/2, no haste) during their main phase. Even though Act of Treason grants the creature haste explicitly in its text, the Bears gain haste and CAN attack. But if the effect granting control had no haste clause — say a hypothetical control-steal spell with no haste — the Bears could not attack that turn.

In summary: check whether the control-stealing effect also grants haste. Without haste, summoning sickness prevents the creature from attacking the same turn control changes (CR 302.6, CR 702.10).