What is the ruling on detesting the cursing of Allah and His Messenger in the unseen within one's soul, and does this fall under disbelief (kufr), and what should I do about it?

A believer is exposed to thoughts of disbelief and hypocrisy, but he detests and rejects them, and thus his faith and certainty increase. This is like truth and falsehood; the heart of a believer does not accept disbelief, and faith remains within it. The Companions complained to the Prophet, peace and blessings be upon him, about the presence of whispers in their hearts, and he said: "That is pure faith," because their hatred and abhorrence of those thoughts indicate their faith. So, you must seek Allah's help against Satan, and as long as you do not succumb to these whispers, there is no blame upon you.