I don't have a particular example, but I can think of all sorts of ways a program could be written to reveal parts of its own source. Your GET example is quite common though (I've seen it in at least one persons graduate project!). Debugging code inadvertantly left in, the program is actually designed to print its own source, the variable's value is displayed as part of an error message, the value is put in a "hidden" field, etc. There are a wide variety of ways to screw things up :-)