When you only have a single tab opened and you receive the error message indicating that you are about to leave the website and the data entered will not be saved and you select "Leave Page", an tab will be created with the url of the page which was just closed. Steps to reproduce the issue: 1. Open Firefox Metro 2. Go to Google docs 3. Open a spreadsheet and start writing 4. Press Windows+Z 5. Select the "X" on the tabs app bar (make sure that's your only tab currently opened). 6. Select "Leave Page" Actual result: After step 6, a new tab is created instead of the existing one. The new tab has no content (blank page) and the url from the previous closed tab (the one at step 3). Expected result: The new tab created after step 6 should display the about:start page and the url should be empty.

This seems to be specific to certain sites. I was able to reproduce on Google Docs but not on StackOverflow.

Mass close of bugs in obsolete product https://bugzilla.mozilla.org/show_bug.cgi?id=1350354