Program: 20932
Project: 20932
Buggy source:
@Override public void handleFree(DownloadLink link) throws Exception {
  requestFileInformation(link);
  br.setFollowRedirects(false);
  String passCode=null;
  String linkurl=null;
  String loginpw=br.getRegex("String_Node_Str").getMatch(0);
  if (br.containsHTML("String_Node_Str") && !(loginpw != null && loginpw.contains("String_Node_Str"))) {
    logger.info("String_Node_Str");
    Form pwform=br.getFormbyProperty("String_Node_Str","String_Node_Str");
    if (pwform == null)     throw new PluginException(LinkStatus.ERROR_PLUGIN_DEFECT);
    if (link.getStringProperty("String_Node_Str",null) == null) {
      passCode=Plugin.getUserInput("String_Node_Str",link);
    }
 else {
      passCode=link.getStringProperty("String_Node_Str",null);
    }
    pwform.put("String_Node_Str",passCode);
    logger.info("String_Node_Str" + passCode + "String_Node_Str");
    br.submitForm(pwform);
    if (br.containsHTML("String_Node_Str") && !(loginpw != null && loginpw.contains("String_Node_Str"))) {
      logger.warning("String_Node_Str" + passCode + "String_Node_Str");
      link.setProperty("String_Node_Str",null);
      throw new PluginException(LinkStatus.ERROR_RETRY);
    }
    linkurl=br.getRedirectLocation();
  }
 else {
    linkurl=br.getRegex("String_Node_Str").getMatch(0);
    if (linkurl == null) {
      linkurl=br.getRegex("String_Node_Str").getMatch(0);
    }
  }
  if (passCode != null) {
    link.setProperty("String_Node_Str",passCode);
  }
  if (linkurl == null)   throw new PluginException(LinkStatus.ERROR_PLUGIN_DEFECT);
  dl=jd.plugins.BrowserAdapter.openDownload(br,link,linkurl,true,-4);
  dl.startDownload();
}

Fixed version (ground truth):
@Override public void handleFree(DownloadLink link) throws Exception {
  requestFileInformation(link);
  br.setFollowRedirects(false);
  String passCode=null;
  String linkurl=null;
  if (br.containsHTML("String_Node_Str")) {
    logger.info("String_Node_Str");
    Form pwform=br.getFormbyProperty("String_Node_Str","String_Node_Str");
    if (pwform == null)     throw new PluginException(LinkStatus.ERROR_PLUGIN_DEFECT);
    if (link.getStringProperty("String_Node_Str",null) == null) {
      passCode=Plugin.getUserInput("String_Node_Str",link);
    }
 else {
      passCode=link.getStringProperty("String_Node_Str",null);
    }
    pwform.put("String_Node_Str",passCode);
    logger.info("String_Node_Str" + passCode + "String_Node_Str");
    br.submitForm(pwform);
    if (br.containsHTML("String_Node_Str")) {
      logger.warning("String_Node_Str" + passCode + "String_Node_Str");
      link.setProperty("String_Node_Str",null);
      throw new PluginException(LinkStatus.ERROR_RETRY);
    }
    linkurl=br.getRedirectLocation();
  }
 else {
    linkurl=br.getRegex("String_Node_Str").getMatch(0);
    if (linkurl == null) {
      linkurl=br.getRegex("String_Node_Str").getMatch(0);
      if (linkurl == null) {
        linkurl=br.getRegex("String_Node_Str").getMatch(0);
      }
    }
  }
  if (passCode != null) {
    link.setProperty("String_Node_Str",passCode);
  }
  if (linkurl == null)   throw new PluginException(LinkStatus.ERROR_PLUGIN_DEFECT);
  dl=jd.plugins.BrowserAdapter.openDownload(br,link,linkurl,true,-4);
  dl.startDownload();
}