App.Actions.MAIL_ACC.enable_unlimited = function(elm, source_elm) {
    $(elm).data('checked', true);
    $(elm).data('prev_value', $(elm).val()); // save prev value in order to restore if needed
    $(elm).val(App.Constants.UNLIM_VALUE);
    $(elm).attr('disabled', true);
    $(source_elm).css('opacity', '1');
}
The web application does not, or can not, sufficiently verify whether a well-formed, valid, consistent request was intentionally provided by the user who submitted the request.