I'm not sure that it could really prove dangerous; there are many 'dangers' in the sense of your account being drained but I'm not sure how the concept of the card 'proving dangerous' is really justifiable. It could, I guess, be used to buy things which would, in turn, damage people but it seems a rather odd expression to use.
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Persian LearnerWhat does it mean that the card could prove dangerous?It means it could be dangerous, or it could eventually end up being dangerous.