Probably forced update as you are running a insecure and unsupported browser.

So "Never" actually means "Not unless we decide your software is insecure or unsupported, when we'll do what we like?" Even Microsoft gives you a choice of whether you update your software.

Actually in Windows 10 you do not. This is a free service you are getting from Mozilla and the program remains theirs.

You need to figure out what your going to do as all browsers have rushed out a patch and Microsoft has released a patch and Intel and AMD and Apple is already patched, phones, tablets, laptops ...everything needs to be patched.

Was in all the major headlines the last few days, CBS, NBC, everywhere. http://money.cnn.com/2018/01/04/technology/spectre-meltdown-cpu-flaws-explainer/index.html

57.0.4 https://www.mozilla.org/firefox/all/ and Firefox Extended Release Version https://www.mozilla.org/en-US/firefox/organizations/all/ (where you should be) will be patched on the 23rd I think

Since you do not need help with a Firefox Issue and this is Volunteer Support as we have no control over this , I suggest you submit suggestions for new or changed features, may I suggest: Feedback: https://qsurvey.mozilla.com/s3/FirefoxInput/

Thanks for your help.

ffsm2 said

Thanks for your help.

Welcome. Please Mark this as Solved with the Solution that Answered your Question so others can find the answer. Thank You.

The extension author of "Theme Font & Size Changer for Thunderbird" has a newer update (Jan 11) as it should work now. The previous version had a datebomb expiration by the author for it to stop working on January 5th.

https://addons.mozilla.org/thunderbird/addon/theme-font-size-changer-for-tb/ https://addons.mozilla.org/thunderbird/addon/theme-font-size-changer-for-tb/versions/

There is a separate preferences for extension updates in Firefox. With this setting, you'll find a section in the lower left of the Add-ons page called Available Updates that you can review at your leisure (example screenshot attached).

(1) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button promising to be careful or accepting the risk.

(2) In the search box above the list, type or paste ext*up and pause while the list is filtered

This is the combination of settings I suggest:

• extensions.update.autoUpdateDefault => false (modified)
• extensions.update.enabled => true (default)

Thanks everyone for your help. The change in Theme & Font Changer was the most obvious symptom rather than the whole problem, I saw it in other extensions too, but I have updated the extension as suggested. My extensions.update.autoUpdateDefault was already set to false, however when I trawled through the config myself, I found settings called app.update.enabled & app.update.log, set to true & false respectively. I don't know what they do, but have toggled them both, & haven't yet had the problem recur.

ffsm2 said

when I trawled through the config myself, I found settings called app.update.enabled & app.update.log, set to true & false respectively.

app.update.enabled determines whether Firefox checks for updates to itself.