Am I obligated to inform my husband or the other party about the adultery I committed, despite my repentance and remorse, fearing that my repentance may not be accepted, and despite my fear of the consequences of disclosure?

A sound repentance erases what came before it, and the one who repents from a sin is like one who has no sin. Allah rejoices at the repentance of His servant and replaces his bad deeds with good ones. Repentance is achieved by abandoning the sin, regretting it, and resolving not to return to it, while concealing oneself; for the Prophet, peace and blessings be upon him, said: "Whoever commits any of these abominable acts, let him conceal himself with the concealment of Allah."

Do not tell your husband or anyone else what happened, and beware of communicating with the person with whom you committed the unlawful act. Conceal yourself, strive in righteous deeds, and be gladdened by the acceptance of your repentance and the pardon and forgiveness of Allah.