User Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:68.0) Gecko/20100101 Firefox/68.0
Steps to reproduce:
I use firefox with the "Restore previous session" option and have multiple tabs open. When a new version is automatically installed in the background and I select a new tab I get a notification "sorry we need to restart firefox" that replaces the page in the tab clicked on. I click the button to do restart and apply the upgrade.
Firefox restarts, and the tab that had the upgrade notification is now set to an empty page.
Firefox restarts and the tab is restored to the page it was on before the notification to restart was shown.