Is it permissible to eat leftover food from female students that would spoil if left untouched and without anyone's knowledge, or is that considered stealing?

It is permissible to take food that has been abandoned willingly and to benefit from it without the owner's permission, according to the statements of Ibn Qudamah and Al-Buhuti. However, if it is not known whether she abandoned it willingly, then it is not permissible to take it without her permission.