User-Agent: Mozilla/5.0 (Windows NT 6.0; WOW64; rv:2.0) Gecko/20100101 Firefox/4.0 Build Identifier: Mozilla/5.0 (Windows NT 6.0; WOW64; rv:2.0) Gecko/20100101 Firefox/4.0 When opening up Firefox 4 with about:home as the standard default home location and the "Restore Previous Session" is available. Instead of clicking it and going straight into panorama view and closing all the tab groups and exiting panorama view, a blank new tab appears. When clicking the home button to load up the about:home location and then choosing "Restore Previous Session", Firefox 4 crashes without notification to the user. Reproducible: Always Steps to Reproduce: 1. have about:home as the default home location 2. click the home button to load the about:home location 3. exit firefox 4. Open up firefox 5. Go to Panorama view 6. Close tab group using the x icon 7. exit panorama view 8. a blank new tab appears 9. click the home button in the toolbar to load about:home 10. choose "restore previous session" on the home page 11. firefox 4 crashes and closes without warning Actual Results: the browser exited without notification to the user or crash notification. Expected Results: the previous session, if available is restored, in this case, the about:home page would be loaded since it was what appeared in the tab we had open when we last exited the browser I havent investigated further about any vulnerabilities this could cause due to this crash such as possible security breach or running remote code etc.

(In reply to comment #2) > bp-d153a99d-c40e-477f-8449-f07412110327 Disregard this trace for this issue, this trace is not for 645461. It is not creating a stack trace nor is the crash reporter appearing. I am attempting to get a trace using an alternative method.

Confirmed on Mozilla/5.0 (Windows NT 6.1; rv:2.2a1pre) Gecko/20110328 Firefox/4.2a1pre After step 10, Firefox crashes without any warning.

Marking new per comment 5.

Confirming with given STR. Will be fixed by bug 650573.

The browser does _not_ crash. Firefox gets accidentally closed with the last tab.

Mozilla/5.0 (X11; Linux i686; rv:7.0a1) Gecko/20110620 Firefox/7.0a1 I followed the steps to reproduce from Comment 0, but the 'Restore previous session' didn't come up so it was impossible for me to verify this issue.