@HomeNotifier 

Hi, do you see any unknown client on your router's client list? And how do you confirm a user was able to login your router? and did you enable remote management on the router?
 

To improve your network security, you could try the following steps:

1) enable access control whitelist and only allow your own client devices to connect the router.

2) change the login password of the router and change your wireless password

3) disable remote management if it is not necessary for you