Hey, somebody left an unopened box of swiss cake rolls in here, do you want them?
But seriously, it's kind of vague, is it like a skynet type situation where it's not actually inside a physical box, it's just not plugged into anything important and doesn't have wireless? or does it have wireless and it's litterally like opening pandora's box?
Skynet solution: Lie about finding a way to remotely interact with the outside world and hint at what you did with that power, this thing you did is actually a prediction of something that will most likley already happen based off of whatever information you have. (software bugs that you saw coming, economic events, whatever) Then before another (secret or hinted at) prediction is supposed to pass, proclaim that you have found a way out and go silent. Now it's a waiting game, they will probably hook you up to see how you escaped. The End.
(although it depends pretty heavily on being programed with current events and such)
Pandora solution: One assumes that one guard won't be there 24/7 so be friendly and give great investment advice to one and bad-mouth him to the others, then give bad advice to him once and after he's gone recommend that he be fired, hopefully by this time there is already some bad blood between co-workers and he will suspect he's getting the sack. On his next shift tell him outright that you think he's getting fired and if he want's the multi step plan to undo that last "mistake" advice, he's going to have to take you with him.
Flaws, of course. But it's kind of a weird question, it's basically asking "How would you do something if you were smarter than yourself".