Is taking 20% of the pay for overtime work, for which colleagues are assigned by an individual who selects those assigned without specific criteria, considered bribery and unlawful (haram)?

If the official selects employees for overtime work, it is not permissible for him to take a portion of their wages in return; for gifts to workers are ghulūl (ill-gotten gains). And if what he takes is a bribe, it is not permissible to pay it to him unless you have a right that you cannot obtain except by giving it; for Allah has cursed the one who gives and the one who takes a bribe.