This article helps affected users in reporting of Firefox and Thunderbird bugs and ease package maintainers fixing them.
Figuring out whose fault is it
Some crashes and problems come from installed addons or 3rd party plugins. To determine if that's the case run Mozilla products with -safe-mode parameter:
firefox -safe-mode
or
thunderbird -safe-mode
Then Disable all add-ons needs to be checked and Make Changes and Restart pressed.
This setting disables all your add-ons and plugins until you manually re-enable them.
If problem still persist it isn't most likely related to addons or plugins and you can proceed to Bugs in gecko. Otherwise go to Reporting addons and plugins issues. . In that case proceed to Plugins and Addons problems section.
Reporting addons and plugins issues
At first don't forget to reenable all plugins and addons in Tools/Add-ons/Extensions and Plugins menu and restart application. Then set your location to about:plugins page, save it and attach to bug report. This page contains information about all installed plugins and it may help developers in resolving your issue. Attach also output of following commands: