@Scotts023 

Change your TP-Link ID password, and make sure it is not easily guessed or shared.

To change your password you can log out of the Deco app, then select the options that you forgot your password and change it: https://www.tp-link.com/us/support/faq/1442/

Tap on the top left menu to access the panel to log out.

@Tony Thank You - I've changed the password but can't someone just get the app and create their own account for the same deco units/network that we're using in the house?  

@Scotts023 

If you are also facing that, I would secure your phone with a password as well. Aside from family in-house should you lose your phone that would be a concern.

@Tony My son has his own phone. Would he be able to get the app on his phone and simply set up his own account for the router we have. Or does the app limit that to only one log-in?

@Scotts023 

No, if your son does not know your TP-Link ID and password. 

So if he downloads the app, he will have the choice to either logging into an existing TP-Link ID or create a new one. If he was to log in with your existing ID then the Deco network will pop up.

If he creates his own ID, then he will see an empty dashboard to add a Deco, similar to what you saw when you first started installing your Deco. 

Now he can't just add the existing Deco because it is bound to your account, he will need to reset each Deco unit manually (hold reset button below for 1 second). Once all default, then add all the nodes to his app.

@Tony perfect - thank you very much for your answers and time.