Program: 57929
Project: 57929
Buggy source:
@EventHandler(ignoreCancelled=true,priority=EventPriority.HIGHEST) public void playerCommand(PlayerCommandPreprocessEvent event){
  String msg=event.getMessage().toLowerCase().replaceAll("String_Node_Str","String_Node_Str").trim();
  if (msg.isEmpty()) {
    return;
  }
  String[] split=msg.split("String_Node_Str");
  PluginCommand cmd=Bukkit.getServer().getPluginCommand(split[0]);
  if (cmd == null) {
    if (split[0].equals("String_Node_Str") || split[0].equals("String_Node_Str")) {
      Player player=event.getPlayer();
      if (Settings.USE_PLOTME_ALIAS) {
        player.performCommand("String_Node_Str" + StringMan.join(Arrays.copyOfRange(split,1,split.length),"String_Node_Str"));
      }
 else {
        MainUtil.sendMessage(BukkitUtil.getPlayer(player),C.NOT_USING_PLOTME);
      }
      event.setCancelled(true);
      return;
    }
  }
  Player player=event.getPlayer();
  PlotPlayer pp=BukkitUtil.getPlayer(player);
  Plot plot=pp.getCurrentPlot();
  if (plot == null) {
    return;
  }
  Optional<List<String>> flag=plot.getFlag(Flags.BLOCKED_CMDS);
  if (flag.isPresent() && !Permissions.hasPermission(pp,C.PERMISSION_ADMIN_INTERACT_BLOCKED_CMDS)) {
    List<String> blocked_cmds=flag.get();
    String[] parts=msg.split("String_Node_Str");
    String c=parts[0];
    if (parts[0].contains("String_Node_Str")) {
      c=parts[0].split("String_Node_Str")[1];
      msg=msg.replace(parts[0].split("String_Node_Str")[0] + "String_Node_Str","String_Node_Str");
    }
    String l=c;
    List<String> aliases=new ArrayList<>();
    for (    HelpTopic cmdLabel : Bukkit.getServer().getHelpMap().getHelpTopics()) {
      if (c.equals(cmdLabel.getName())) {
        break;
      }
      String label=cmdLabel.getName().replaceFirst("String_Node_Str","String_Node_Str");
      if (aliases.contains(label)) {
        continue;
      }
      PluginCommand p;
      if ((p=Bukkit.getPluginCommand(label)) != null) {
        for (        String a : p.getAliases()) {
          if (aliases.contains(a)) {
            continue;
          }
          aliases.add(a);
          a=a.replaceFirst("String_Node_Str","String_Node_Str");
          if (!a.equals(label) && a.equals(c)) {
            c=label;
            break;
          }
        }
      }
    }
    if (!l.equals(c)) {
      msg=msg.replace(l,c);
    }
    for (    String s : blocked_cmds) {
      Pattern pattern;
      if (!RegExUtil.compiledPatterns.containsKey(s)) {
        RegExUtil.compiledPatterns.put(s,pattern=Pattern.compile(s));
      }
 else {
        pattern=RegExUtil.compiledPatterns.get(s);
      }
      if (pattern.matcher(msg).matches()) {
        MainUtil.sendMessage(pp,C.COMMAND_BLOCKED);
        String perm;
        if (plot.isAdded(pp.getUUID())) {
          perm="String_Node_Str";
        }
 else {
          perm="String_Node_Str";
        }
        if (!Permissions.hasPermission(pp,perm)) {
          event.setCancelled(true);
        }
        return;
      }
    }
  }
}

Fixed version (ground truth):
@EventHandler(ignoreCancelled=true,priority=EventPriority.HIGHEST) public void playerCommand(PlayerCommandPreprocessEvent event){
  String msg=event.getMessage().toLowerCase().replaceAll("String_Node_Str","String_Node_Str").trim();
  if (msg.isEmpty()) {
    return;
  }
  String[] split=msg.split("String_Node_Str");
  PluginCommand cmd=Bukkit.getServer().getPluginCommand(split[0]);
  if (cmd == null) {
    if (split[0].equals("String_Node_Str") || split[0].equals("String_Node_Str")) {
      Player player=event.getPlayer();
      if (Settings.USE_PLOTME_ALIAS) {
        player.performCommand("String_Node_Str" + StringMan.join(Arrays.copyOfRange(split,1,split.length),"String_Node_Str"));
      }
 else {
        MainUtil.sendMessage(BukkitUtil.getPlayer(player),C.NOT_USING_PLOTME);
      }
      event.setCancelled(true);
      return;
    }
  }
  Player player=event.getPlayer();
  PlotPlayer pp=BukkitUtil.getPlayer(player);
  Plot plot=pp.getCurrentPlot();
  if (plot == null) {
    return;
  }
  Optional<List<String>> flag=plot.getFlag(Flags.BLOCKED_CMDS);
  if (flag.isPresent() && !Permissions.hasPermission(pp,C.PERMISSION_ADMIN_INTERACT_BLOCKED_CMDS)) {
    List<String> blocked_cmds=flag.get();
    String[] parts=msg.split("String_Node_Str");
    String c=parts[0];
    if (parts[0].contains("String_Node_Str")) {
      c=parts[0].split("String_Node_Str")[1];
      msg=msg.replace(parts[0].split("String_Node_Str")[0] + ':',"String_Node_Str");
    }
    String l=c;
    List<String> aliases=new ArrayList<>();
    for (    HelpTopic cmdLabel : Bukkit.getServer().getHelpMap().getHelpTopics()) {
      if (c.equals(cmdLabel.getName())) {
        break;
      }
      String label=cmdLabel.getName().replaceFirst("String_Node_Str","String_Node_Str");
      if (aliases.contains(label)) {
        continue;
      }
      PluginCommand p;
      if ((p=Bukkit.getPluginCommand(label)) != null) {
        for (        String a : p.getAliases()) {
          if (aliases.contains(a)) {
            continue;
          }
          aliases.add(a);
          a=a.replaceFirst("String_Node_Str","String_Node_Str");
          if (!a.equals(label) && a.equals(c)) {
            c=label;
            break;
          }
        }
      }
    }
    if (!l.equals(c)) {
      msg=msg.replace(l,c);
    }
    for (    String s : blocked_cmds) {
      Pattern pattern;
      if (!RegExUtil.compiledPatterns.containsKey(s)) {
        RegExUtil.compiledPatterns.put(s,pattern=Pattern.compile(s));
      }
 else {
        pattern=RegExUtil.compiledPatterns.get(s);
      }
      if (pattern.matcher(msg).matches()) {
        MainUtil.sendMessage(pp,C.COMMAND_BLOCKED);
        String perm;
        if (plot.isAdded(pp.getUUID())) {
          perm="String_Node_Str";
        }
 else {
          perm="String_Node_Str";
        }
        if (!Permissions.hasPermission(pp,perm)) {
          event.setCancelled(true);
        }
        return;
      }
    }
  }
}