@Redout007 

 TP-Link range extender repeats router's wifi signal and  uses the same Wi-Fi password and wifi security as the router after being configured successfully. 

That means if router is an Open or Unsecured wifi network, wif of range extender is also an open network.  

May I know if router wifi network is secured and what is wireless security type the router is using?(on router wireless page)

If you wish to secure range extender while router wifi network is unsecured, you could try to consider wire RE to router via ethernet cable and use it as an Access Point.  How to connect TP-Link Wi-fi Extender to Router with Ethernet Cable (Access Point Mode）