Can't play on Firefox

[riderodd]

Since the last week the player API won't work (even the embed won't play in fact) in Firefox.

I can even reproduce it on the API Playground: https://w.soundcloud.com/player/api_playground.html
Or in the first embed I found on SC.com home: https://w.soundcloud.com/player/?url=https%3A//api.soundcloud.com/tracks/252231083&auto_play=true&hide_related=false&show_comments=true&show_user=true&show_reposts=false&visual=true
The only things that shows is the gray logo, and nothing happens:

Tested on Firefox 50.1