I have noticed that _too many_ sites are not working properly in Firefox 47.0.1.
After hours of work, I discovered that the culprit is setting media.peerconnection.enabled to false. Doing this disables WebRTC, which is generally a good idea for both privacy and security reasons.
Interestingly, none of the failing sites actually use WebRTC.
This issue seems to be the result of incredibly poorly coded libraries that a number of popular sites use.
Just as an example, take a close look at Airbnb. When media.peerconnection.enabled is set to false, it becomes impossible to set the dates for reservations on their main page.
Although diagnosing the problem took a fair amount of effort, finding a solution may require even more effort. Globally enabling WebRTC is a bad idea for many reasons, but disabling it is breaking popular sites.
Looking forward to a good discussion regarding this issue.
This should be reported also on firefox bugzilla account
As a stop gap measure, I recommend this extension add: media.peerconnection.ice.default_address_only directly under media.peerconnection.enabled.
For another discussion of this issue, see: ChrisAntaki/disable-webrtc-firefox#9
fixes #21 and #55
Since the VPN leakage is still under question, I added both prefs. In full privacy mode, both prefs are changed. But in the compatible mode we are only alteringedia.peerconnection.ice.default_address_only
@Gitoffthelawn thanks for the report
You're welcome. What you did sounds great. I'll take a look at it in a few days when I have a moment.