[Plugin: phpbb_recent_topics] Links, cookies, log in

Hi guys. I have a site with domain name pindosiya.com and my forum has separate domain usbb.us When I click on the widget in the side bar I get to the forum page, but the url I get is https://pindosiya.com/usbb.us/viewtopic.php?p=24341#p24341

Just because I have pindosiya.com in front of the usbb.us the cookies are not saved by browser and my users have to login again to the forum.

How do I remove the domain name of my site (pindosiya.com) where people click on the widget, so when people click on forum they get straight to usbb.us?

https://www.ads-software.com/extend/plugins/phpbb-recent-topics/