User Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:23.0) Gecko/20100101 Firefox/23.0 (Beta/Release) Build ID: 20130803192641 Steps to reproduce: [1] Lots of browsing, multiple open windows and tabs. [2] Intended to close current tab (Ctrl-W), accidentally hit Ctrl-Q, which is one key left. Actual results: Browser shut down immediately, closing all windows and tabs, without confirmation. It appeared to have crashed. Expected results: Firefox should have asked for confirmation before exiting. Or even better, it should ignore Ctrl-Q entirely, leaving Quit as a menu operation without an accelerator key.