Getting the same errors, this is with and without extensions, and I made sure Java was up to date.

My Java is up to date too

Guys, the problem is most likely with some of your plugins. I started FireFox in safe mode with all my plugins disabled (menu Help) and the problem with JavaScript syntax error disappeared.

This issue can be caused by an extension that isn't working properly.
Another user has reported that the Social Fixer extension caused this issue.

Start Firefox in Safe Mode to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance).

• Do not click the Reset button on the Safe mode start window or otherwise make changes.

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

Same issue with latest upgrade. In Safe Mode removed SocialFixer. That fixed the problem.

I have the same problem but it happens on pages that are not on facebook, (like pages on Oprah.com) which tells me its NOT socialfixer, or not JUST to do with socialfixer.

My java is also up-to-date.

I was getting the Syntax Error (Javascript ap.) in Gmail (Start Page). After disabling Integrated Gmail 2.8.8, All back to normal !

I still have the problem. Is there a way that Firefox can fix the problem from their end, for those of us who aren't that technically savvy?

I would like you to first try Safe Mode. Do not confuse this with Windows safe mode. Read here: https://support.mozilla.org/kb/Safe+Mode If you can operate your browser, you should be able to get into Safe Mode. Reading is knowledge, thus read the link first. Once you achieve Safe Mode, report back to us on the forum with your results. Good Luck!

Thanks, DriftMGR, for contacting me so quickly. I clicked the Restart Firefox button. Now everything looks very different, but happy to say that Error Message isn't popping up all the time anymore. May take a while to adjust to all the other changes, but I will manage. Thank you

Ok, so it turns out that for me it really was socialfixer. There was an upgrade on Tuesday and I just found out about it today. All better for me.  :)

Now my Adblock isn't working anymore. Groan. That has always been one of my favorite things about Fire Fox. No ads. Any advice on how to get Adblock working again?

Hi summertime

Try to ask advice at the Adblock Plus forum.

• https://adblockplus.org/forum/

46 views and 0 answers on the Adblock Plus forum :-(

Social Fixer was the culprit in my case. The problem has been fixed in their version 7.3.

Same problem (and solution) here with the syntax errors happening not only on facebook, but other sites like IMBD etc.

Social fixer was the problem and updating it resolved the issue, the version available via the Add-ons Manager is still the old one but the version available from the socialfixer.com is working fine.

@ summertime, FWIW I'm using ABP without issue.

Thanks people.

I changed to Safe Mode and It solved the problem. But how can I discover wich plugin (or plugins) or extension is causing the problem? thanks in advance.

With all plug ins disabled, you can add them back one by one. Restart when needed. Continue this process until you find the non-compatible plug-in.

Ok, and I discovered that the extension that was producing the error message was "Linkify (for Microsoft Lync) 1.0. I I excluded it and I didn't receive the error message longer. Thanks for the help. Very very thanks. Antonio Carlos.

google social fixer 7.3 and download it. fixed the problem for me as well.