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 core. Otherwise go to #Reporting_addons_and_plugins_issues.
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 (by File/Save Page As...) to file and attach it to bug report. This page contains information about all installed plugins and it may help us in resolving your issue. Attach also output of following commands:
rpm -q firefox xulrunner flash-plugin gnash google-talkplugin nspluginwrapper ls /usr/lib64/mozilla/plugins/ ls /usr/lib/mozilla/plugins/
You may also run Firefox or Thunderbird by strace. This help us to track which dynamic libraries are loaded during startup. Strace usage:
strace firefox &>strace_output
or in case of Thunderbird:
strace thunderbird &> strace_output
and don't forget to attach created strace_output file to bug report.