There is a use-after-free that appears to be related to rendering the display based on multiple scripts. A PoC is attached, tested on Windows only. Note the PoC is somewhat unreliable on some browsers, sometimes it needs to render a minute or two in the foreground before crashing. This is related to unreliability in the freed object being reallocated as a value that causes the crash, not unreliability in the underlying bug (it crashes immediately in a debug build of Flash). With enough effort, an attacker could likely trigger the issue immediately.
Proof of Concept: