Streaming audio from various websites cease to function after the upgrade (on two computers). One site http://saleminteractivemedia.com/ListenLive/Player/WWTCAM says: libavcodec may be vulnerable and is not supported, and should be updated to play video. Podbean sites say: No compatible source was found for this media. Some sites just do nothing. I do not know if there is a way to upgrade libavcodec in Ubuntu. The news release of Firefox 50.0 says it "Blocked versions of libavcodec older than 54.35.1"