Apparently typing the following string into almost any application on OS X Mountain Lion will crash it:

File:///

(The "F" must be uppercase)

Tried it at the apple store today and it works perfectly! Suck it "Geniuses".

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Heard about that. I think it'll crash Safari, too, so a website can force a user's browser to crash if they happen to be running Safari on OS X Mountain Lion.

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Random Word Generator

From what I read, any application that uses the standard "NSTextField" for text input (which is probably almost any app that you can enter text into) is affected.

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I remember my roommate playing around with that. We didn't have all the right details, so he only ended up crashing the searchbar with it, but knowing it could be used to crash just about anything could lead to some fun.

I'm really not a Mac fan (that being said, I'm writing this reply on one...), so I like to think that I'm eating into Apple's profits by having a bunch of laptops in the store showing error messages, putting people off buying one!

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Haha, I feel you there. If I can keep this trick in mind, I'll definitely be doing the same whenever I have the chance.