What is the ruling on money gained from selling the contents of a "mystery box" that I purchased through gharar (excessive uncertainty), and is it permissible to sell the remaining contents?

Purchasing a box or container whose contents are unknown is a gharar (uncertainty) sale, which is Islamically invalid. An invalid sale must be reversed unless it has become irrevocable. If an invalid sale becomes irrevocable through another sale, alteration, or damage, scholars differ on its ruling. Imam Shafi'i holds that reversal is always obligatory, while Imam Malik and Abu Hanifa maintain that the value becomes binding. Irrevocability occurs when the item's essence changes, market prices fluctuate, it is sold, a defect occurs, or a third-party right becomes attached to it. Since the sale in question has become irrevocable by the sale of half its contents, and given that it occurred in a country where Islamic law is not enforced, the questioner should estimate the fair value of the box if its contents were known. If this value is higher than what was paid, the difference should be returned to the seller, or his forgiveness sought, or the amount given in charity.