Program: 20979
Project: 20979
Buggy source:
@Override public void handlePremium(DownloadLink downloadLink,Account account) throws Exception {
  String finalfn=downloadLink.getName();
  requestFileInformation(downloadLink);
  if (account != null) {
    login(account);
    br.getPage(downloadLink.getDownloadURL());
  }
  String downloadurl;
  String steplink=br.getRegex("String_Node_Str").getMatch(0);
  if (steplink == null) {
    downloadurl=br.getRegex("String_Node_Str").getMatch(0);
    if (downloadurl == null) {
      downloadurl=br.getRegex("String_Node_Str").getMatch(0);
    }
    if (downloadurl == null) {
      downloadurl=br.getRegex("String_Node_Str").getMatch(0);
    }
    if (downloadurl == null) {
      throw new PluginException(LinkStatus.ERROR_FATAL);
    }
  }
 else {
    downloadurl="String_Node_Str" + steplink;
    br.getPage(downloadurl);
    Form capform=br.getFormbyProperty("String_Node_Str","String_Node_Str");
    if (capform == null) {
      String form2search=br.getRegex("String_Node_Str").getMatch(0);
      if (form2search == null)       throw new PluginException(LinkStatus.ERROR_PLUGIN_DEFEKT);
      capform=br.getFormbyProperty("String_Node_Str",form2search);
    }
    int i=0;
    Browser brc=br.cloneBrowser();
    while (capform != null) {
      String pagepiece=br.getRegex("String_Node_Str").getMatch(0);
      if (pagepiece == null)       throw new PluginException(LinkStatus.ERROR_PLUGIN_DEFEKT);
      String[] captchalinks=HTMLParser.getHttpLinks(pagepiece,"String_Node_Str");
      if (captchalinks == null || captchalinks.length == 0)       throw new PluginException(LinkStatus.ERROR_PLUGIN_DEFEKT);
      String adr=null;
      File file=null;
      for (      String link : captchalinks) {
        URLConnectionAdapter con=brc.openGetConnection(link);
        if ((con.getContentType().contains("String_Node_Str"))) {
          adr=link;
          file=this.getLocalCaptchaFile();
          Browser.download(file,con);
          break;
        }
        con.disconnect();
        continue;
      }
      if (adr == null || file == null)       throw new PluginException(LinkStatus.ERROR_PLUGIN_DEFEKT);
      String code=getCaptchaCode(file,downloadLink);
      capform.getInputFieldByName("String_Node_Str").setValue(code);
      br.submitForm(capform);
      capform=br.getFormbyProperty("String_Node_Str","String_Node_Str");
      i++;
      if (i > 3) {
        throw new PluginException(LinkStatus.ERROR_CAPTCHA);
      }
    }
    if (capform != null)     throw new PluginException(LinkStatus.ERROR_PLUGIN_DEFEKT);
    br.setFollowRedirects(false);
    steplink=br.getRegex("String_Node_Str").getMatch(0);
    if (steplink == null) {
      throw new PluginException(LinkStatus.ERROR_RETRY);
    }
    downloadurl="String_Node_Str" + steplink;
    br.getPage(downloadurl);
    if (br.getRedirectLocation() == null || br.getRedirectLocation().contains("String_Node_Str")) {
      throw new PluginException(LinkStatus.ERROR_RETRY);
    }
    downloadurl=br.getRedirectLocation();
    if (downloadurl == null) {
      throw new PluginException(LinkStatus.ERROR_RETRY);
    }
  }
  downloadurl=downloadurl.replaceAll("String_Node_Str","String_Node_Str");
  br.setFollowRedirects(true);
  br.setDebug(true);
  downloadLink.setDownloadSize(0);
  dl=jd.plugins.BrowserAdapter.openDownload(br,downloadLink,downloadurl,false,1);
  if (dl.getConnection().getContentType().contains("String_Node_Str")) {
    dl.getConnection().disconnect();
    throw new PluginException(LinkStatus.ERROR_FATAL,JDL.L("String_Node_Str","String_Node_Str"));
  }
  downloadLink.setFinalFileName(finalfn);
  dl.startDownload();
}

Fixed version (ground truth):
@Override public void handlePremium(DownloadLink downloadLink,Account account) throws Exception {
  String finalfn=downloadLink.getName();
  requestFileInformation(downloadLink);
  if (account != null) {
    login(account);
    br.getPage(downloadLink.getDownloadURL());
  }
  String downloadurl;
  String steplink=br.getRegex("String_Node_Str").getMatch(0);
  if (steplink == null) {
    downloadurl=br.getRegex("String_Node_Str").getMatch(0);
    if (downloadurl == null) {
      downloadurl=br.getRegex("String_Node_Str").getMatch(0);
    }
    if (downloadurl == null) {
      downloadurl=br.getRegex("String_Node_Str").getMatch(0);
    }
    if (downloadurl == null) {
      throw new PluginException(LinkStatus.ERROR_FATAL);
    }
  }
 else {
    downloadurl="String_Node_Str" + steplink;
    br.getPage(downloadurl);
    downloadurl=br.getRegex("String_Node_Str").getMatch(0);
    Form capform=br.getFormbyProperty("String_Node_Str","String_Node_Str");
    if (capform == null) {
      String form2search=br.getRegex("String_Node_Str").getMatch(0);
      if (form2search != null) {
        capform=br.getFormbyProperty("String_Node_Str",form2search);
      }
    }
    if (downloadurl == null && capform != null) {
      int i=0;
      Browser brc=br.cloneBrowser();
      while (capform != null) {
        String pagepiece=br.getRegex("String_Node_Str").getMatch(0);
        if (pagepiece == null)         throw new PluginException(LinkStatus.ERROR_PLUGIN_DEFEKT);
        String[] captchalinks=HTMLParser.getHttpLinks(pagepiece,"String_Node_Str");
        if (captchalinks == null || captchalinks.length == 0)         throw new PluginException(LinkStatus.ERROR_PLUGIN_DEFEKT);
        String adr=null;
        File file=null;
        for (        String link : captchalinks) {
          URLConnectionAdapter con=brc.openGetConnection(link);
          if ((con.getContentType().contains("String_Node_Str"))) {
            adr=link;
            file=this.getLocalCaptchaFile();
            Browser.download(file,con);
            break;
          }
          con.disconnect();
          continue;
        }
        if (adr == null || file == null)         throw new PluginException(LinkStatus.ERROR_PLUGIN_DEFEKT);
        String code=getCaptchaCode(file,downloadLink);
        capform.getInputFieldByName("String_Node_Str").setValue(code);
        br.submitForm(capform);
        capform=br.getFormbyProperty("String_Node_Str","String_Node_Str");
        i++;
        if (i > 3) {
          throw new PluginException(LinkStatus.ERROR_CAPTCHA);
        }
      }
      if (capform != null)       throw new PluginException(LinkStatus.ERROR_PLUGIN_DEFEKT);
    }
    br.setFollowRedirects(false);
    steplink=br.getRegex("String_Node_Str").getMatch(0);
    if (steplink == null) {
      throw new PluginException(LinkStatus.ERROR_RETRY);
    }
    downloadurl="String_Node_Str" + steplink;
    br.getPage(downloadurl);
    if (br.getRedirectLocation() == null || br.getRedirectLocation().contains("String_Node_Str")) {
      throw new PluginException(LinkStatus.ERROR_RETRY);
    }
    downloadurl=br.getRedirectLocation();
    if (downloadurl == null) {
      throw new PluginException(LinkStatus.ERROR_RETRY);
    }
  }
  downloadurl=downloadurl.replaceAll("String_Node_Str","String_Node_Str");
  br.setFollowRedirects(true);
  br.setDebug(true);
  downloadLink.setDownloadSize(0);
  dl=jd.plugins.BrowserAdapter.openDownload(br,downloadLink,downloadurl,false,1);
  if (dl.getConnection().getContentType().contains("String_Node_Str")) {
    dl.getConnection().disconnect();
    throw new PluginException(LinkStatus.ERROR_FATAL,JDL.L("String_Node_Str","String_Node_Str"));
  }
  downloadLink.setFinalFileName(finalfn);
  dl.startDownload();
}