jitsi-meet: SecurityError for video call in iframe if 3rd party cookies are disabled

When trying to embed a meet.jit.si in an iframe in the current Firefox Developer Edition (47.0a2), the video conference fails to function correctly. The console shows:

DOMException [SecurityError: "The operation is insecure."
code: 18
nsresult: 0x80530012
location: https://meet.jit.si/libs/lib-jitsi-meet.min.js?v=825:9

When I first load the iframe, I’m prompted to share microphone and video which I allow. My video appears in the list at the bottom, but is not sent to the room, other clients connected to the room do not see me as present, and I do not see any other clients in the room.

In this state, if I attempt to use “Chat”, I am prompted to enter a nickname. After entering the nickname, Firefox shows the error:

SecurityError: The operation is insecure.
    setDisplayName()     app.bundle.min.js:7
...

If I enter it a second time, it appears to succeed, but with the error Unable to init avatar - no id printed in the console. If I then attempt to send a chat message, the error Error: Your message was not sent. is displayed in the message pane.

This only seems to happen in iframes – loading meet.jit.si with a full window works.