Router is a Surf SOHO HW2 running firmware 7.1.1 build 3102
In Advanced -> Content blocking -> Web blocking there is an entry for adnexus.net as shown below.
I have recently been running a Windows program that logs all TCP/UDP connections. Its called TcpLogView from here
It has caught a few instances of a browser opening a connection to a computer at adnexus.net on port 443. For example
A screen shot of the details is below. The URL is cut off, but it ends with adnexus.net
Am I missing something or is this a bug?