Is money acquired from a salary increase due to a certificate obtained with the help of leaked exam questions considered illicit money (haram), what is the ruling on this money, and what must be done to purify the money and possessions?

Obtaining a certificate in this manner involves deception, forgery, and defrauding one of the parties. The one who does this must seek forgiveness and make sincere repentance. As for the employee's promotion and salary increase based on it, if the company is aware of this method and the employee is competent and performs his job skillfully, then the salary and increase are not forbidden for him.