How a tiny XML file can unleash a billion laughs

Also known as an XML entity expansion attack, this vulnerability is beautifully malicious. A hacker writes a tiny text file where 'lol' is defined as ten 'lol's, and those ten are defined as ten more, compounding recursively. When the parser tries to read it, it geometrically multiplies the word until the server's brain absolutely implodes under the weight of a billion laughs.