Автор рассказывает, что наши ублюдки хакеры:

использовали уязвимости Microsoft Exchange ProxyShell и ProxyLogon для скачивания файла

а не

получили удаленный доступ и "I-own-the-server-motherfucker!"

public class SAXHandler extends DefaultHandler {
    private static final String CLASSNAME = "class";
    private Object object;
    private String element;
    private Logger logger;

    public SAXHandler() {
        logger = LogManager.getLogger(this.getClass().getName());
    }
    //...
    @Override
    public void characters(char[] chars, int start, int length) {
        if (element != null) {
            String s = new String(chars, start, length);
            try {
                ReflectionHelper.setFieldValue(object, element, s);
            } catch (...) {
                //...
            }
        }

    }
    //...
}

public class ReflectionHelper {
    private static ReflectionHelper helper;

    public static ReflectionHelper instance() {
        if (helper == null)
            helper = new ReflectionHelper();
        return helper;
    }

    public static Object createInstance(String className) throws
            ClassNotFoundException,
            IllegalAccessException,
            InstantiationException {
        return Class.forName(className).newInstance();
    }

    public static <T> void setFieldValue(Object object, String fieldName, T value)
            throws NoSuchFieldException, IllegalArgumentException, IllegalAccessException {

        Field field = object.getClass().getDeclaredField(fieldName);
        field.setAccessible(true);
        if (field.getType().equals(value.getClass())) {
            field.set(object, value);
        } else {
            throw new IllegalArgumentException();
        }
        field.setAccessible(false);

    }
}