title: User X receives response from user Y (IIS)
body: <p>We have a web application (ASP.NET) that uses AJAX calls to return information from a certain row that is presented on a web page, in this case product information. Our users sometimes experience strange behaviour in which one user clicks a product info link (client side javascript/jquery that sends out an AJAX call and shows a popup displaying the result) and then suddenly the pop up shows not only a different product, but also information from another user. It is not reproducable. When the user clicks the link a second time, everything is OK.</p>
  
  <p>In our application logging we can see that the information that is returned to the user is not random. At the exact same time, at the exact same web server (we use load balancing) user Y is requesting info for a product that then seems to be sent to user X. </p>
  
  <p>In this scenario both users are inside a VPN on two different locations in which they have a different IP-address in the 10.X range. Interestingly enough they have the same internal IP address. As a work-around we now return a JSON result object and compare the returned product id and user id with the product id and user id from the request.</p>
  
  <p>Does anyone recognize this behaviour? If so, what can we do to stop this from happening? </p>