I just ran into this issue today as well. After reading this thread I opened a chat with QB Support. First they tried to tell me that feature (to open attachments in a new browser window) was only available in the US. (I'm in Canada.) When I informed them that feature HAD been available to me until Nov. 8, they did some more checking and came back to say the backend team had changed that in the latest update. Here's hoping if enough of us complain about it, they'll change it back.