Program: 1969
Project: 1969
Buggy source:
@Override public void onEntityTarget(EntityTargetEvent event){
  if (NPCManager.isNPC(event.getTarget())) {
    event.setCancelled(true);
  }
  if (!(event instanceof NPCEntityTargetEvent)) {
    return;
  }
  NPCEntityTargetEvent e=(NPCEntityTargetEvent)event;
  HumanNPC npc=NPCManager.get(e.getEntity());
  if (npc != null && event.getTarget() instanceof Player) {
    if (e.getNpcReason() == NpcTargetReason.NPC_RIGHTCLICKED) {
      Player p=(Player)event.getTarget();
      if (plugin.validateTool("String_Node_Str",p.getItemInHand().getTypeId(),p.isSneaking()) == true) {
        if (!NPCManager.validateSelected(p,npc.getUID())) {
          NPCManager.selectedNPCs.put(p.getName(),npc.getUID());
          p.sendMessage(ChatColor.GREEN + "String_Node_Str" + StringUtils.wrap(npc.getStrippedName())+ "String_Node_Str"+ StringUtils.wrap("String_Node_Str" + npc.getUID())+ "String_Node_Str");
          return;
        }
      }
      if (plugin.validateTool("String_Node_Str",p.getItemInHand().getTypeId(),p.isSneaking()) == true) {
        CitizensBasicNPCEvent ev=new CitizensBasicNPCEvent(npc.getName(),MessageUtils.getText(npc,(Player)e.getTarget(),plugin),npc,Reason.RIGHT_CLICK,(Player)e.getTarget());
        plugin.getServer().getPluginManager().callEvent(ev);
      }
      if (npc.isTrader()) {
        TraderInterface.handleRightClick(npc,p);
      }
      if (npc.isWizard()) {
        if (Permission.hasPermission("String_Node_Str",(CommandSender)p)) {
          if (p.getItemInHand().getTypeId() == Constants.wizardInteractItem) {
            if (npc.getWizard().getNumberOfLocations() > 0) {
              npc.getWizard().buyTeleport(p,npc.getWizard(),Operation.WIZARD_TELEPORT);
            }
          }
        }
 else {
          p.sendMessage(MessageUtils.noPermissionsMessage);
        }
      }
      if (npc.isBlacksmith()) {
        if (Permission.hasPermission("String_Node_Str",(CommandSender)p)) {
          if (npc.getBlacksmith().getToolType(p.getItemInHand()).equals("String_Node_Str")) {
            npc.getBlacksmith().buyItemRepair(p,npc,p.getItemInHand(),Operation.BLACKSMITH_TOOL_REPAIR);
          }
 else           if (npc.getBlacksmith().getToolType(p.getItemInHand()).equals("String_Node_Str")) {
            npc.getBlacksmith().buyItemRepair(p,npc,p.getItemInHand(),Operation.BLACKSMITH_ARMOR_REPAIR);
          }
        }
 else {
          p.sendMessage(MessageUtils.noPermissionsMessage);
        }
      }
      if (npc.isBandit()) {
        BanditInterface.handleRightClick(npc,p);
      }
      if (npc.isEvil()) {
        if (p.getItemInHand().getTypeId() == Constants.evilNPCTameItem) {
        }
      }
    }
  }
}

Fixed version (ground truth):
@Override public void onEntityTarget(EntityTargetEvent event){
  if (NPCManager.isNPC(event.getTarget())) {
    event.setCancelled(true);
  }
  if (!(event instanceof NPCEntityTargetEvent)) {
    return;
  }
  NPCEntityTargetEvent e=(NPCEntityTargetEvent)event;
  HumanNPC npc=NPCManager.get(e.getEntity());
  if (npc != null && event.getTarget() instanceof Player) {
    if (e.getNpcReason() == NpcTargetReason.NPC_RIGHTCLICKED) {
      Player p=(Player)event.getTarget();
      if (plugin.validateTool("String_Node_Str",p.getItemInHand().getTypeId(),p.isSneaking()) == true) {
        if (!NPCManager.validateSelected(p,npc.getUID())) {
          NPCManager.selectedNPCs.put(p.getName(),npc.getUID());
          p.sendMessage(ChatColor.GREEN + "String_Node_Str" + StringUtils.wrap(npc.getStrippedName())+ "String_Node_Str"+ StringUtils.wrap("String_Node_Str" + npc.getUID())+ "String_Node_Str");
          return;
        }
      }
      if (plugin.validateTool("String_Node_Str",p.getItemInHand().getTypeId(),p.isSneaking()) == true) {
        CitizensBasicNPCEvent ev=new CitizensBasicNPCEvent(npc.getName(),MessageUtils.getText(npc,(Player)e.getTarget(),plugin),npc,Reason.RIGHT_CLICK,(Player)e.getTarget());
        plugin.getServer().getPluginManager().callEvent(ev);
      }
      if (npc.isTrader()) {
        TraderInterface.handleRightClick(npc,p);
      }
      if (npc.isWizard()) {
        if (Permission.hasPermission("String_Node_Str",(CommandSender)p)) {
          if (p.getItemInHand().getTypeId() == Constants.wizardInteractItem) {
            if (npc.getWizard().getNumberOfLocations() > 0) {
              npc.getWizard().buyTeleport(p,npc.getWizard(),Operation.WIZARD_TELEPORT);
            }
          }
        }
 else {
          p.sendMessage(MessageUtils.noPermissionsMessage);
        }
      }
      if (npc.isBlacksmith()) {
        if (Permission.hasPermission("String_Node_Str",(CommandSender)p)) {
          if (npc.getBlacksmith().getToolType(p.getItemInHand()).equals("String_Node_Str")) {
            npc.getBlacksmith().buyItemRepair(p,npc,p.getItemInHand(),Operation.BLACKSMITH_TOOLREPAIR);
          }
 else           if (npc.getBlacksmith().getToolType(p.getItemInHand()).equals("String_Node_Str")) {
            npc.getBlacksmith().buyItemRepair(p,npc,p.getItemInHand(),Operation.BLACKSMITH_ARMORREPAIR);
          }
        }
 else {
          p.sendMessage(MessageUtils.noPermissionsMessage);
        }
      }
      if (npc.isBandit()) {
        BanditInterface.handleRightClick(npc,p);
      }
      if (npc.isEvil()) {
        if (p.getItemInHand().getTypeId() == Constants.evilNPCTameItem) {
        }
      }
    }
  }
}