Question

How can I decode this JS? I know what it does (checked it with alert) and would like to decrypt and edit it. How can I do it?

What type of encryption is this? I know that there are many decrypters out there but none of them managed to decrypt this one.

BTW I am a newbie.

function xViewState() {
    var a = 0,
        m, v, t, z, x = new Array('9091968376', '8887918192818786347374918784939277359287883421333333338896', '877886888787', '949990793917947998942577939317'),
        l = x.length;
    while (++a <= l) {
        m = x[l - a];
        t = z = '';
        for (v = 0; v < m.length;) {
            t += m.charAt(v++);
            if (t.length == 2) {
                z += String.fromCharCode(parseInt(t) + 25 - l + a);
                t = '';
            }
        }
        x[l - a] = z;
    }
    document.write('<' + x[0] + ' ' + x[4] + '>.' + x[2] + '{' + x[1] + '}</' + x[0] + '>');
}
xViewState();

Answer 1

This isn’t encryption, it’s obfuscation. Now you know what it writes out, lose the obfuscation and just write out what you want instead…

document.write('<style undefined>.yourstylename{position:absolute;top:-9999px}</style>');

The obfuscation works by simply listing the ASCII codes for everything involved, offset by about 20 (varies per array element), represented as a 2 digit decimal number. It’s very basic.

Thus:

"style"
-> 115, 116, 121, 108, 101 (ASCII codes)
-> 90, 91, 96, 83, 76 (offset of 25 in this case)