会话变量不是特定于一个用户的

i have two ASP.net systems, both of them use the same DB and are on the same server, I keep the user id in session variables, unfortunately, i noticed that in the finance system, some payments are made by a sales person on which it was supposed to be done by cashier. How is that possible? Does ASP.Net scatter the session variables between different users? i have two ASP.net systems, both of them use th