Assalamu'alaykum. I've been wondering. If someone purchased an object that contains something forbidden, and the purchase becomes forbidden, too, does that mean he doesn't own the object at all? So he is not allowed to use it in lawful ways, either? What should he do then?My second question is, are we allowed to buy an object that is predominantly lawful, even though it contains some forbidden things? For example, buying a game that contains cross picture, but it's just there and the player can just ignore it.

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

If the forbidden thing that is in the item you purchased was not intended in the contract (i.e., the reason for buying the item), and one can benefit from it in a lawful way, then it is not a sin if one benefits from it in a lawful manner. For example, if someone buys a game that has music in it, then he can mute the sound and benefit from the game. This also applies to the cross, provided one can remove it (erase or cover it), and avoid it while playing the game.

Ibn Uthaymeen was asked about the ruling on a game that includes a cross, and he said: “One must cover (erase or remove) the cross, and break it if it cannot be removed or covered. Know that if a young child gets used to seeing the cross repeatedly, then he will take the matter lightly, and the more one becomes exposed to something, the weaker his feelings (of resentment and repulsion) towards become. Therefore, it is mandatory upon us to protect our children and keep them away from anything that has a cross, whether this is on the computer or small toy cars with which they play, because some of these toys have a cross on the side or the back. It is an obligation upon us to protect our children from this.” [End of quote]

Allah knows best.