cheeseburger_menu.css in Cheeseburger Menu 8

.cheeseburger-menu__menu-list-item >ul {
    transition: all 0.25s ease-in-out;
}
.cheeseburger-menu__menu-list-item > ul.open-parent {
    height: auto !important;
    overflow: auto !important;
}

.cheeseburger-menu__menu-list-item > ul.open-parent ul.open-parent.open-child{
    height: auto !important;
    overflow: auto !important;
}