How to hide local lan IP

RouterOS Beginner Basics
1

Visiting web sites that show my external IP I see my internal IP too.
How to hide my local LAN addresses from being discovered by external services?
What the masquerading rule should I add to Firewall filter and what order it must have?

Now my IP Firewall filters rules are as follows:

 0    ;;; default configuration
      chain=input action=accept protocol=icmp log=no log-prefix="" 

 1    ;;; default configuration
      chain=input action=accept connection-state=established,related log=no log-prefix="" 

 2    ;;; default configuration
      chain=input action=drop in-interface=ether1-wan log=no log-prefix="" 

 3    ;;; default configuration
      chain=forward action=accept connection-state=established,related log=no log-prefix="" 

 4    ;;; default configuration
      chain=forward action=drop connection-state=invalid log=no log-prefix="" 

 5    ;;; default configuration
      chain=forward action=drop connection-state=new connection-nat-state=!dstnat in-interface=ether1-wan log=no log-prefix=""
2

I don’t think it’s leaking through router. Usually it’s detected using things in your browser (Flash, Java, WebRTC, …).