Apparently typing "File:///" (minus the quote marks) on a Mac running on the Mountain Lion operating system will crash your computer.
According to Open Radar, the capital F is an important factor and by the time you hit the third "/", down everything goes.
One commenter on the community bug report stated they tried filing a report about the issue with Crash Reporter UI but just typing it in there cause Crash Reporter to go down itself. This means that people running on OS X can't even report the issue.
Gizmodo tried it out on a MacBook running on the 10.7.1 operation system and found the issue doesn't occur there, indicating it's likely just a Mountain Lion issue. MacRumors tested the bug further and found that the final character in the 8-character string doesn't even need to be a forward slash. It stated that almost any character after "File://" will cause everything to crash. Interestingly, MacRumors also found that typing speed seems to be a factor as well.
"[L]eaving a brief pause between typing // and the next character will prevent the crash from occurring," MacRumors stated.
Mac OS X users, now you know.
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