Dwitter Vision by tomxor

function u(t) {

c.width=1920 // clear the canvas
for(i=0;i<9;i++)
x.fillRect(400+i*100+S(t)*300,400,50,200) // draw 50x200 rects

} // 122/140

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    u(t) is called 60 times per second.
    t: Elapsed time in seconds.
    S: Shorthand for Math.sin.
    C: Shorthand for Math.cos.
    T: Shorthand for Math.tan.
    R: Function that generates rgba-strings, usage ex.: R(255, 255, 255, 0.5)
    c: A 1920x1080 canvas.
    x: A 2D context for that canvas.

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tomxor

function u(t) {

t>1&&eval('U='+parent[c.style=9*u.r|reset()].u);U(t);if(t%1>.8)for(c.width=128,i=1e4;i--;)x.fillRect(i&127,0|i/120-t*4,1,u.r=Math.random())

Mar 13 2020 1:15 AM UTC

}// 139/140

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Dwitter Vision

Show more comments…
u/Xen

love the idea
u/DaSpider

ReferenceError: U is not defined
u/KilledByAPixel

how is this possible?
u/tomxor

All loaded iframes are enumerated on the window object (for any webpage), the value is the window object of the corresponding frame... and from inside a dweet this can be accessed (with restrictions) by going to the parent frame, then you have access to any globals in that other frame. While you can't call a function since it's in a different JS context, you can read it's source and re-evaluate it.
u/tomxor

essentually window.parent[n].u is the function created by dwitter for dweet n on the page, if you add it to a string it calls toString which returns the source, you can eval this and assign it to something to run in this context.
u/tomxor

I think I am the most verbose person here sorry :/
u/jellyedwards

Wow that's amazing!
u/jellyedwards

Very nice presentation of that little trick
u/katkip

nice trickery. #exploit #trick #hack
u/sigveseb

Woah


      u(t) is called 60 times per second.
      t: elapsed time in seconds.
      c: A 1920x1080 canvas.
      x: A 2D context for that canvas.
      S: Math.sin
      C: Math.cos
      T: Math.tan
      R: Generates rgba-strings, ex.: R(255, 255, 255, 0.5)

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