Hi there, tturleys.
At his time, there's no reported case for other users who encountered fake trojan scam pop-up message. This scam message appears in the form of a pop-up window claiming that your computer has been infected and you need to take urgent action to get rid of it.
You can try closing the tab or window of the browser that hosted the pop-up. You can also open the Task Manager to end all running trojan application.
If you need further assistance, I'd suggest contacting your IT guy. They'll help you remove the pop-up message from appearing again when opening QuickBooks Online.
Please reply to this post if you need anything else. I'm here to help.
