Recently i got a very strange behavior on our WIFI network: We share a WIFI network with a simple router. One of us pays the bills and he's the one, who got the management account from our ISP. So if i want to log in to watch my mobile bills (the ISP does both, mobile and wired internet stuff; i have my own account) i am logged in automatically with his internet management account, from different devices over the WIFI.
How can this be possible? I can not find useful information about that. As i know from a programmers point of view, simple session management should avoid such a behavior (eg. cookies). Does it mean, that the session management is only server sided and just bound to ip (server, programming issue)?
I think the ISP bound the external IP of our router automatically to this single management account, which would be, in my opinion, a very big issue (watching bills, changing address data and so on.).