get_xdg_var (XDG_Var xdg) {
    const gchar* actual_value = getenv (xdg.environmental);
    const gchar* home         = getenv ("HOME");
    gchar* return_value;

    if (! actual_value || strcmp (actual_value, "") == 0) {
        if (xdg.default_value) {
            return_value = str_replace ("~", home, xdg.default_value);
        } else {
            return_value = NULL;
        }
    } else {
        return_value = str_replace("~", home, actual_value);
    }

    return return_value;
}

This category addresses vulnerabilities caused by flawed access control mechanisms, where incorrect permission settings allow unauthorized users to access restricted resources.