According to Open Radar, a newly filed bug report has shown Mac users that the potential to crash the majority of apps on OS X can be found by simply typing a line of text. Just by typing File:/// with a capital letter, most apps will crash, and an error report for you app will appear on the screen.
Currently it’s unknown why this bug happens, but at first it was thought to be caused by an error within the OS’s built-in spellchecker, however this was later found to be unlikely as the crash still happened within text boxes that don’t support the spellchecker such as the Safari location search. All Macs currently running Mountain Lion seem to be affected by this bug, whilst all other versions of Mac OS seem to be unaffected.
It’s not a major issue as it’s rare that a Mac user may need to type in the text ‘File:///,’ however it may have opened up a window of concern towards some users as unsaved content may be affected by the crash. Likely though, the bug will be fixed soon enough.[Source]