Is it permissible or impermissible to request a box containing a sum of money, claimed by a refugee widow after her husband’s death, from a protection company and have it transferred to the questioner’s personal account for later investment?

Do not rush to receive the box until you have verified the matter and consulted experts. The company only hands over the box to its owner, or to their agent with a duly notarized legal power of attorney, or to their heirs upon proof of their inheritance. The woman's request for you to receive the box is unusual, as the company will not hand it over to you unless you have a valid legal power of attorney proving your agency on behalf of the heirs and that they are indeed the man's heirs. If you have the documents and are certain of the woman's honesty, then there is no blame upon you.