One of the headline changes in Firefox 42 is adding a tracking blocker in private browsing windows. That kind of filtering may affect embedded social site features.

If you are using private windows, you can turn off the anti-tracking feature on the Options page as a test. This article has more information on where to find that setting: What happened to Tracking Protection?.

If the problem occurs in regular windows, hmm... I think you already tested in Firefox's Safe Mode, but if not:

In Safe Mode, Firefox deactivates extensions, hardware acceleration, and some other advanced features to help you assess whether these are causing the problem.

If Firefox is not running: Hold down the Shift key when starting Firefox.

If Firefox is running: You can restart Firefox in Safe Mode using either:

• "3-bar" menu button > "?" button > Restart with Add-ons Disabled
• Help menu > Restart with Add-ons Disabled

and OK the restart.

Both scenarios: A small dialog should appear. Click "Start in Safe Mode" (not Refresh).

Any improvement?

Switching off the anti-tracking feature via the Options page certainly solves the problem - both Facebook and Twitter embeds are now visible and functional on the webpage in question. However, my concern is that others who visit this website (which I manage) using Firefox will have the same problem but will not know why, or what to do about it, and will not make full use of our homepage. This seems a potentially widespread problem. Can you either fix this at the next update, or advise me if there is anything I can do to prevent visitors to my website from having blank FB and TW spaces on our homepage?

I don't think this feature is going to be switched off, but then, I can't always predict the future.

Perhaps there is a convenient way to display some alternate content in the blank areas. Could you provide a link to the page?

Alternative content won't really compensate for the loss of embedded links. The whole point is to make our home page a one-stop site for all our media. The website is: www.brightonpalestinecampaign.org

Well, I see what you mean (screen shots attached, normal vs. private). But my thought was that perhaps you could show alternate content that educates your visitors about the tracking protection feature and how they can turn it off if they like. Let me see what I can come up with.

The script in this demo page isn't very elegant: after 3 seconds, it checks for blank iframes or unreplaced Twitter timeline links and displays a notification. Maybe something along these lines.

https://jeffersonscher.com/res/fx42tracktwitter.html

(Compare a regular and a private window)

Thanks for your ideas. Two quick points. First, the scripts you refer to were actually provided by Facebook and Twitter, specifically for embedding links to their sites. So, if they are inelegant I guess the criticism should be directed at them. Second, it seems clear that as long as FB and TW track users, some Firefox users whose Tracking Protection is switched on will find embedded links to FB and TW blank or with limited functionality. These giants aren't going to change their settings, so it would be good if Firefox adjusted the settings for their Tracking Protection to allow tracking when launching these very widely used social media sites.

Hi Bazzie, when Tracking Protection kicks in, users should have access to create an exception for all the trackers in the current page using the shield icon on the toolbar. There isn't, to my knowledge, a plan to allow/disallow individual trackers.

Regarding "inelegant", I was referring to my workaround script in my demo page. I'm sure you can come up with something better if you think about it. I noticed that it still gives the message even after I make an exception because of the long time required to load Twitter content, so the script isn't waiting long enough...