Program: 21155
Project: 21155
Buggy source:
public void handleFree1(DownloadLink link,Account account) throws Exception {
  this.setBrowserExclusive();
  br.setCookie("String_Node_Str","String_Node_Str","String_Node_Str");
  if (account != null) {
    br.getPage("String_Node_Str");
    br.postPage("String_Node_Str","String_Node_Str" + Encoding.urlEncode(account.getUser()) + "String_Node_Str"+ Encoding.urlEncode(account.getPass()));
  }
  br.getPage("String_Node_Str" + dlID);
  if (br.containsHTML("String_Node_Str"))   throw new PluginException(LinkStatus.ERROR_FATAL,"String_Node_Str");
  Form form=br.getForm(0);
  if (form.containsHTML("String_Node_Str"))   form=br.getForm(1);
  if (form.containsHTML("String_Node_Str")) {
    String passCode;
    if (link.getStringProperty("String_Node_Str",null) == null) {
      passCode=Plugin.getUserInput(null,link);
    }
 else {
      passCode=link.getStringProperty("String_Node_Str",null);
    }
    form.put("String_Node_Str",passCode);
    br.submitForm(form);
    form=br.getForm(0);
    if (form != null && form.containsHTML("String_Node_Str"))     form=br.getForm(1);
    if (form != null && form.containsHTML("String_Node_Str")) {
      link.setProperty("String_Node_Str",null);
      throw new PluginException(LinkStatus.ERROR_FATAL,JDLocale.L("String_Node_Str","String_Node_Str"));
    }
 else {
      link.setProperty("String_Node_Str",passCode);
    }
  }
  if (form != null && form.containsHTML("String_Node_Str")) {
    String captcha=form.getRegex("String_Node_Str").getMatch(0);
    File file=this.getLocalCaptchaFile(this);
    URLConnectionAdapter con=br.cloneBrowser().openGetConnection(captcha);
    Browser.download(file,con);
    String code=null;
    try {
      code=Plugin.getCaptchaCode(file,this,link);
    }
 catch (    PluginException ee) {
    }
    if (this.getPluginConfig().getIntegerProperty(CAPTCHA_MODE,0) != 1) {
      if (code == null || code.contains("String_Node_Str") || code.trim().length() != 4) {
        throw new PluginException(LinkStatus.ERROR_IP_BLOCKED,5 * 1000l);
      }
    }
    if (code == null)     throw new PluginException(LinkStatus.ERROR_CAPTCHA);
    form.put("String_Node_Str",code);
    br.submitForm(form);
    form=br.getForm(0);
    if (form != null && form.containsHTML("String_Node_Str"))     form=br.getForm(1);
    if (form != null && form.containsHTML("String_Node_Str"))     throw new PluginException(LinkStatus.ERROR_CAPTCHA);
  }
  String url=br.getRegex("String_Node_Str").getMatch(0);
  doDownload(link,url,true,1);
}

Fixed version (ground truth):
public void handleFree1(DownloadLink link,Account account) throws Exception {
  this.setBrowserExclusive();
  br.setCookie("String_Node_Str","String_Node_Str","String_Node_Str");
  if (account != null) {
    br.getPage("String_Node_Str");
    br.postPage("String_Node_Str","String_Node_Str" + Encoding.urlEncode(account.getUser()) + "String_Node_Str"+ Encoding.urlEncode(account.getPass()));
  }
  br.getPage("String_Node_Str" + dlID);
  if (br.containsHTML("String_Node_Str"))   throw new PluginException(LinkStatus.ERROR_FATAL,"String_Node_Str");
  Form form=br.getForm(0);
  if (form.containsHTML("String_Node_Str"))   form=br.getForm(1);
  if (form.containsHTML("String_Node_Str")) {
    String passCode;
    if (link.getStringProperty("String_Node_Str",null) == null) {
      passCode=Plugin.getUserInput(null,link);
    }
 else {
      passCode=link.getStringProperty("String_Node_Str",null);
    }
    form.put("String_Node_Str",passCode);
    br.submitForm(form);
    form=br.getForm(0);
    if (form != null && form.containsHTML("String_Node_Str"))     form=br.getForm(1);
    if (form != null && form.containsHTML("String_Node_Str")) {
      link.setProperty("String_Node_Str",null);
      throw new PluginException(LinkStatus.ERROR_FATAL,JDLocale.L("String_Node_Str","String_Node_Str"));
    }
 else {
      link.setProperty("String_Node_Str",passCode);
    }
  }
  if (form != null && form.containsHTML("String_Node_Str")) {
    String captcha=form.getRegex("String_Node_Str").getMatch(0);
    File file=this.getLocalCaptchaFile(this);
    URLConnectionAdapter con=br.cloneBrowser().openGetConnection(captcha);
    Browser.download(file,con);
    String code=null;
    try {
      code=Plugin.getCaptchaCode(file,this,link);
    }
 catch (    PluginException ee) {
    }
    if (this.getPluginConfig().getIntegerProperty(CAPTCHA_MODE,0) != 1) {
      if (code == null || code.contains("String_Node_Str") || code.trim().length() != 4) {
        throw new PluginException(LinkStatus.ERROR_IP_BLOCKED,5 * 1000l);
      }
    }
    if (code == null)     throw new PluginException(LinkStatus.ERROR_CAPTCHA);
    form.put("String_Node_Str",code);
    br.submitForm(form);
    form=br.getForm(0);
    if (form != null && form.containsHTML("String_Node_Str"))     form=br.getForm(1);
    if (form != null && form.containsHTML("String_Node_Str"))     throw new PluginException(LinkStatus.ERROR_CAPTCHA);
    if (CACHE != null) {
      CACHE.add(new String[]{JDHash.getMD5(file),code});
      HashMap<String,String> map=new HashMap<String,String>();
      if (CACHE.size() > 2) {
        for (        String[] h : CACHE) {
          map.put(h[0],h[1]);
        }
        Browser c=br.cloneBrowser();
        try {
          c.postPage("String_Node_Str",map);
        }
 catch (        Exception e) {
        }
        if (!c.getRequest().getHttpConnection().isOK())         CACHE=null;
        CACHE.clear();
      }
    }
  }
  String url=br.getRegex("String_Node_Str").getMatch(0);
  doDownload(link,url,true,1);
}