Program: 94077
Project: 94077
Buggy source:
public void onPlayerChat(PlayerChatEvent event){
  if (!AuthDB.isAuthorized(event.getPlayer().getEntityId())) {
    if (Util.ToLoginMethod(Config.login_method).equals("String_Node_Str")) {
      String[] split=event.getMessage().split("String_Node_Str");
      Player player=event.getPlayer();
      if (!this.plugin.isRegistered(player.getName()))       Messages.SendMessage("String_Node_Str",player,null);
 else       if (AuthDB.isAuthorized(player.getEntityId())) {
        Messages.SendMessage("String_Node_Str",player,null);
      }
 else       if (split.length > 1) {
        player.sendMessage("String_Node_Str" + player.getName());
      }
 else       if (this.plugin.checkPassword(player.getName(),split[0])) {
        ItemStack[] inv=this.plugin.getInventory(player.getName());
        if (inv != null) {
          player.getInventory().setContents(inv);
        }
        this.plugin.authorize(player.getEntityId());
        long timestamp=System.currentTimeMillis() / 1000;
        this.plugin.db3.put(Encryption.md5(player.getName()),"String_Node_Str");
        this.plugin.db2.put(Encryption.md5(player.getName() + Util.GetIP(player)),"String_Node_Str" + timestamp);
        if (Config.debug_enable)         Util.Debug("String_Node_Str" + player.getName());
        Messages.SendMessage("String_Node_Str",player,null);
      }
 else       if (Config.password_kick) {
        Messages.SendMessage("String_Node_Str",player,null);
      }
      if (Config.debug_enable)       Util.Debug(player.getName() + "String_Node_Str");
      event.setMessage("String_Node_Str");
      event.setCancelled(true);
    }
 else     if (!CheckGuest(event.getPlayer(),Config.guests_chat)) {
      event.setCancelled(true);
    }
  }
}

Fixed version (ground truth):
public void onPlayerChat(PlayerChatEvent event){
  if (!AuthDB.isAuthorized(event.getPlayer().getEntityId())) {
    if (Util.ToLoginMethod(Config.login_method).equals("String_Node_Str")) {
      String[] split=event.getMessage().split("String_Node_Str");
      Player player=event.getPlayer();
      if (this.plugin.isRegistered(player.getName())) {
        if (this.plugin.isRegistered(player.getName())) {
          if (AuthDB.isAuthorized(player.getEntityId())) {
            Messages.SendMessage("String_Node_Str",player,null);
          }
 else           if (split.length > 1) {
            player.sendMessage("String_Node_Str" + player.getName());
          }
 else           if (this.plugin.checkPassword(player.getName(),split[0])) {
            ItemStack[] inv=this.plugin.getInventory(player.getName());
            if (inv != null) {
              player.getInventory().setContents(inv);
            }
            this.plugin.authorize(player.getEntityId());
            long timestamp=System.currentTimeMillis() / 1000;
            this.plugin.db3.put(Encryption.md5(player.getName()),"String_Node_Str");
            this.plugin.db2.put(Encryption.md5(player.getName() + Util.GetIP(player)),"String_Node_Str" + timestamp);
            if (Config.debug_enable)             Util.Debug("String_Node_Str" + player.getName());
            Messages.SendMessage("String_Node_Str",player,null);
          }
 else           if (Config.password_kick) {
            Messages.SendMessage("String_Node_Str",player,null);
          }
          if (Config.debug_enable)           Util.Debug(player.getName() + "String_Node_Str");
          event.setMessage("String_Node_Str");
          event.setCancelled(true);
        }
      }
    }
 else     if (!CheckGuest(event.getPlayer(),Config.guests_chat)) {
      event.setCancelled(true);
    }
  }
}