If you have the same DNS (ip) and login on different ports, with different username and pass, then your plugin totally blocking access to second and above login to page.
x.x.x.x:8000 with user:bla; pass bla -> working
x.x.x.x:8001 with user:bla1; pass bla1 -> can not login apsolutlly on page, the request for login do not comes out!
x.x.x.x:8002 with user:bla2; pass bla2 -> can not login apsolutlly on page, the request for login do not comes out!
and so on..
If I disable plugin or close the firefox in same moment the windows with login pop-up.