When using Firefox 66.0.2 on MacOS Mojave 10.14.4, when i click links from applications, it opens it 2nd tab When I open Firefox normally y the application, it just opens one tab (in this case depending on the option set) But when i click on links in applications (Thunderbird, Apple mail etc). the browser opens: The firx tab is blank, while the second ta displays the page from the clicked link. Disabling "Open links in tabs instead of new windows" under Preference "help" but doesn't solve the issue as it opens in a new window rather than a 2nd tab. Is there an about:config option i could set?