I have documented this extensively in the other thread and believe I found a root cause.

Repeatable behavior if you clear your cookies correctly:
http://www.opserver.de/ubb7/ubbthreads.php?ubb=showflat&Number=474505#Post474505

I managed to single out and block the two(2) malicious javascripts, thus ending the unwanted behavior on my personal browser only:
http://www.opserver.de/ubb7/ubbthreads.php?ubb=showflat&Number=474507#Post474507

Root cause found in (hacked?) ubb scripting, which launches the two(2) malicious javascripts:
http://www.opserver.de/ubb7/ubbthreads.php?ubb=showflat&Number=474547#Post474547

Can you spot the one evil line of code?
http://www.opserver.de/ubb7/ubb_js/image.js

Hint: here is the same script, from the horse's mouth:
https://www.ubbcentral.com/forums/ubb_js/image.js