Program: 20896
Project: 20896
Buggy source:
@Override public void handleFree(DownloadLink link) throws Exception {
  this.setBrowserExclusive();
  br.getHeaders().put("String_Node_Str",RandomUserAgent.generate());
  br.getPage(link.getDownloadURL());
  if (br.containsHTML("String_Node_Str"))   throw new PluginException(LinkStatus.ERROR_IP_BLOCKED,60 * 60 * 1001l);
  if (br.containsHTML("String_Node_Str"))   throw new PluginException(LinkStatus.ERROR_FILE_NOT_FOUND);
  String dllink=br.getRegex("String_Node_Str").getMatch(0);
  if (dllink == null)   throw new PluginException(LinkStatus.ERROR_PLUGIN_DEFECT);
  br.setDebug(true);
  dl=jd.plugins.BrowserAdapter.openDownload(br,link,dllink,true,1);
  URLConnectionAdapter con=dl.getConnection();
  if (con.getContentType().contains("String_Node_Str")) {
    br.followConnection();
synchronized (LOCK) {
      if (counter > 10) {
        counter=0;
        throw new PluginException(LinkStatus.ERROR_HOSTER_TEMPORARILY_UNAVAILABLE,30 * 60 * 1000l);
      }
 else {
        counter++;
        throw new PluginException(LinkStatus.ERROR_TEMPORARILY_UNAVAILABLE,30 * 60 * 1000l);
      }
    }
  }
  String correctEnding=LoadImage.getFileType(dllink,dl.getConnection().getContentType());
  String wrongEnding=link.getName().substring(link.getName().lastIndexOf('.'));
  if (correctEnding != null && wrongEnding != null)   link.setFinalFileName(link.getName().replace(wrongEnding,correctEnding));
  dl.startDownload();
}

Fixed version (ground truth):
@Override public void handleFree(DownloadLink link) throws Exception {
  this.setBrowserExclusive();
  br.getHeaders().put("String_Node_Str",RandomUserAgent.generate());
  br.getPage(link.getDownloadURL());
  if (br.containsHTML("String_Node_Str"))   throw new PluginException(LinkStatus.ERROR_TEMPORARILY_UNAVAILABLE,30 * 60 * 1000l);
  if (br.containsHTML("String_Node_Str"))   throw new PluginException(LinkStatus.ERROR_FILE_NOT_FOUND);
  if (br.containsHTML("String_Node_Str")) {
    String url=br.getRedirectLocation() != null ? br.getRedirectLocation() : br.getRegex("String_Node_Str").getMatch(0);
    if (url == null)     throw new PluginException(LinkStatus.ERROR_PLUGIN_DEFECT);
    throw new PluginException(LinkStatus.ERROR_IP_BLOCKED,60 * 60 * 1001l);
  }
  String dllink=br.getRegex("String_Node_Str").getMatch(0);
  if (dllink == null)   throw new PluginException(LinkStatus.ERROR_PLUGIN_DEFECT);
  br.setDebug(true);
  dl=jd.plugins.BrowserAdapter.openDownload(br,link,dllink,true,1);
  URLConnectionAdapter con=dl.getConnection();
  if (con.getContentType().contains("String_Node_Str")) {
    br.followConnection();
synchronized (LOCK) {
      if (counter > 10) {
        counter=0;
        throw new PluginException(LinkStatus.ERROR_HOSTER_TEMPORARILY_UNAVAILABLE,30 * 60 * 1000l);
      }
 else {
        counter++;
        throw new PluginException(LinkStatus.ERROR_TEMPORARILY_UNAVAILABLE,30 * 60 * 1000l);
      }
    }
  }
  String correctEnding=LoadImage.getFileType(dllink,dl.getConnection().getContentType());
  String wrongEnding=null;
  if (link.getName().lastIndexOf('.') > 0)   wrongEnding=link.getName().substring(link.getName().lastIndexOf('.'));
  if (correctEnding != null && wrongEnding != null)   link.setFinalFileName(link.getName().replace(wrongEnding,correctEnding));
  if (correctEnding != null && wrongEnding == null)   link.setFinalFileName(link.getName() + correctEnding);
  dl.startDownload();
}