Program: 20815
Project: 20815
Buggy source:
@Override public void handleFree(DownloadLink downloadLink) throws Exception, PluginException {
  requestFileInformation(downloadLink);
  br.setFollowRedirects(false);
  Form captchaform=br.getFormbyProperty("String_Node_Str","String_Node_Str");
  String captchaurl=br.getRegex("String_Node_Str").getMatch(0);
  if (captchaurl == null)   captchaurl=br.getRegex("String_Node_Str").getMatch(0);
  if (captchaurl == null || captchaform == null) {
    logger.warning("String_Node_Str");
    throw new PluginException(LinkStatus.ERROR_PLUGIN_DEFECT);
  }
  captchaform.remove(null);
  String passCode=null;
  for (int i=0; i <= 5; i++) {
    if (br.containsHTML("String_Node_Str")) {
      if (downloadLink.getStringProperty("String_Node_Str",null) == null) {
        passCode=Plugin.getUserInput("String_Node_Str",downloadLink);
      }
 else {
        passCode=downloadLink.getStringProperty("String_Node_Str",null);
      }
      captchaform.put("String_Node_Str",passCode);
    }
    String code=getCaptchaCode(captchaurl,downloadLink);
    captchaform.put("String_Node_Str",code);
    br.submitForm(captchaform);
    if (br.containsHTML("String_Node_Str") || br.containsHTML("String_Node_Str")) {
      logger.warning("String_Node_Str");
      downloadLink.setProperty("String_Node_Str",null);
      continue;
    }
    break;
  }
  if (br.containsHTML("String_Node_Str") || br.containsHTML("String_Node_Str")) {
    logger.warning("String_Node_Str");
    downloadLink.setProperty("String_Node_Str",null);
    throw new PluginException(LinkStatus.ERROR_CAPTCHA);
  }
  String domain=br.getRegex("String_Node_Str").getMatch(0);
  String dirname=br.getRegex("String_Node_Str").getMatch(0);
  String basename=br.getRegex("String_Node_Str").getMatch(0);
  if (domain == null || dirname == null || basename == null) {
    logger.warning("String_Node_Str");
    throw new PluginException(LinkStatus.ERROR_PLUGIN_DEFECT);
  }
  String dllink="String_Node_Str" + domain + dirname+ "String_Node_Str"+ basename;
  if (passCode != null) {
    downloadLink.setProperty("String_Node_Str",passCode);
  }
  String ttt=br.getRegex("String_Node_Str").getMatch(0);
  if (ttt != null) {
    int tt=Integer.parseInt(ttt);
    sleep(tt * 1001,downloadLink);
  }
  jd.plugins.BrowserAdapter.openDownload(br,downloadLink,dllink,true,1);
  if (dl.getConnection().getContentType().contains("String_Node_Str")) {
    br.followConnection();
    throw new PluginException(LinkStatus.ERROR_PLUGIN_DEFECT);
  }
  dl.startDownload();
}

Fixed version (ground truth):
@Override public void handleFree(DownloadLink downloadLink) throws Exception, PluginException {
  requestFileInformation(downloadLink);
  br.setFollowRedirects(false);
  Form captchaform=br.getFormbyProperty("String_Node_Str","String_Node_Str");
  String captchaurl=br.getRegex("String_Node_Str").getMatch(0);
  if (captchaurl == null)   captchaurl=br.getRegex("String_Node_Str").getMatch(0);
  if (captchaurl == null || captchaform == null) {
    logger.warning("String_Node_Str");
    throw new PluginException(LinkStatus.ERROR_PLUGIN_DEFECT);
  }
  captchaform.remove(null);
  String passCode=null;
  for (int i=0; i <= 5; i++) {
    if (br.containsHTML("String_Node_Str")) {
      if (downloadLink.getStringProperty("String_Node_Str",null) == null) {
        passCode=Plugin.getUserInput("String_Node_Str",downloadLink);
      }
 else {
        passCode=downloadLink.getStringProperty("String_Node_Str",null);
      }
      captchaform.put("String_Node_Str",passCode);
    }
    String code=getCaptchaCode(captchaurl,downloadLink);
    captchaform.put("String_Node_Str",code);
    br.submitForm(captchaform);
    if (br.containsHTML("String_Node_Str")) {
      logger.warning("String_Node_Str");
      downloadLink.setProperty("String_Node_Str",null);
      continue;
    }
    break;
  }
  if (br.containsHTML("String_Node_Str")) {
    logger.warning("String_Node_Str");
    downloadLink.setProperty("String_Node_Str",null);
    throw new PluginException(LinkStatus.ERROR_CAPTCHA);
  }
  String domain=br.getRegex("String_Node_Str").getMatch(0);
  String dirname=br.getRegex("String_Node_Str").getMatch(0);
  String basename=br.getRegex("String_Node_Str").getMatch(0);
  if (domain == null || dirname == null || basename == null) {
    logger.warning("String_Node_Str");
    throw new PluginException(LinkStatus.ERROR_PLUGIN_DEFECT);
  }
  String dllink="String_Node_Str" + domain + dirname+ "String_Node_Str"+ basename;
  if (passCode != null) {
    downloadLink.setProperty("String_Node_Str",passCode);
  }
  String ttt=br.getRegex("String_Node_Str").getMatch(0);
  if (ttt != null) {
    int tt=Integer.parseInt(ttt);
    sleep(tt * 1001,downloadLink);
  }
  jd.plugins.BrowserAdapter.openDownload(br,downloadLink,dllink,true,1);
  if (dl.getConnection().getContentType().contains("String_Node_Str")) {
    br.followConnection();
    throw new PluginException(LinkStatus.ERROR_PLUGIN_DEFECT);
  }
  dl.startDownload();
}