Is taking what is rightfully yours surreptitiously considered theft or a triumph of justice, if the manager is unjust and has deprived the employee of promotions despite his deserving them?

Whoever is subjected to injustice and deprived of promotion and salary increase, his recourse is to complain about the manager to his superiors or to the judiciary, or to leave the job and seek a better one. It is not permissible for him to take any money secretly, because it is theft and treachery. He has no financial right here except after promotion or agreement on a higher salary. The permissible "taking by force" (ظفر) is taking a fixed material right that could not be obtained through legitimate means, and the questioner does not have a fixed material right.