Is it permissible to disclose the moral flaws of one's ex-husband that led to the divorce, when asked about the reason for the separation, or must one conceal them and remain unmarried?

A Muslim must conceal the faults of his brother, unless silence about an absolute fault of your suitor would deter suitors from you. In that case, it is permissible to mention his fault, provided there is truthfulness, justice, and necessity, and that you limit yourself to the fault that compromises the interest of the marriage. This is not among the forbidden forms of backbiting, as backbiting is permissible if it entails a benefit that is obligatory or permissible to obtain. In matters of marriage, if one is consulted, it is obligatory to clarify the faults, as the Prophet, peace and blessings be upon him, did with Fatimah bint Qays when Mu'awiyah and Abu Jahm proposed to her. He said: "As for Mu'awiyah, he is a destitute man with no wealth, and as for Abu Jahm, he does not put down his stick from his shoulder."