I need to see the network traffic for a particular site of which I have no control. The problem is that the site at one point triggers a pop-up which automatically closes wh
You could set an window close event breakpoint. This way the debugger stops the widnow (popup) from closing.
devtools -> scripts (or sources) -> event listener breakpoints -> Window -> close

Link to Chromium rfc
I use this chrome extension. It has a URL sniffer, which you can open in any window and it'll log all HTTP requests for you.