You may remember in 2019 that all add-ons suddenly stopped working because the certificate used to verify extension signatures expired. It just happened again Friday. I suspect this is the problem. There is no fixed version for Windows XP, but I can suggest a couple workarounds:

(1) Try repeating the 2019 fix by importing the latest certificate (2) Update to the Extended Support Release of Firefox 52 and disable extension verification

Option #1 is safer if it works for you. Also, you might have stopped at 48 for some reason that neither of us can remember right now.

Certificate Import Option

The steps are in the "Manual Import Method" of my old article from the last time:

https://www.jeffersonscher.com/ffu/armagadd-on_2_0.html

For Step 1, you need the newer certificate, which can be found here:

https://searchfox.org/mozilla-release/source/security/manager/ssl/addons-public-intermediate.pem

You can't save that page directly because it's HTML. Instead, you can either:

(A) Manually select, copy, paste the content from lines 1 through 41 into a plain text editor and then save as "addons-public-intermediate.pem" (or a .crt extension is fine, too).

(B) On the right side of the page, click the "R" button next to "Raw". This will load a bare certificate view that you can save normally with Ctrl+S. However, Windows likely will add a .txt extension, so when importing, you need to change the filter to "All Files" (or rename the downloaded file).

Then proceed with the other steps.

Here is a Reddit thread about a Firefox 56 user's experience with this approach: https://old.reddit.com/r/firefox/comments/1jcbdi6/omnija_file_not_working/mi47d6m/

Thanks for your help with this.

I methodically followed your instructions and have confirmed that the new certificate, good through 2100, does appear in the list of certificates. However, when I restarted Firefox, ChatZilla is not available as it has been disabled. The message in the Add-ons manager is "Chatzilla could not be verified for use in FireFox and has been disabled".

Can you help me to get around this?

Thanks!

If you check the Troubleshooting Information page in your Firefox, is there a button on the right side labeled "Clear startup cache..." which restarts Firefox and clears that cache? I'm not sure what version got that button.

If that isn't available, hmm, usually clearing the timestamp and restarting is enough.

Unfortunately, the troubleshooting information page doesn't have a button to do that.

I am at Firefox version 48.0.2 because I believe that is the last version that will work with XP.

Is there any other way to clear the start-up cache? If I delete the cache file (if you know what the file name is) will Firefox recreate it at start-up?

Thanks!

The last version that will work with Windows XP is Firefox 78. BUT - the last version that will work with old extensions like ChatZilla (not updated for Firefox 57+) is Firefox 56 or the Extended Support Release of Firefox 52.

The startup caches are separate from the web content cache, and I don't know where they are.

Sorry, the last version for Windows XP was Firefox 52.9.0esr, not 78. Too many Mac threads this week.

Hi!

I am at Firefox version 48.0.2 because I believe that is the last version that will work with XP and the limitations of the CPU in this old machine.

I have cleared the timestamp and relaunched Firefox several times without success. In desperation, I rebooted the computer several times, as well. The new certificate does appear in the certificate list, so it is certainly in place.

I did find a file named startupCache.4.little in the Documents and Settings folder related to Firefox.

This is where startupCache.4.little resides: Documents and Settings\...\Local Settings\Application Data\Mozilla\Firefox\Profiles\ss17429f.default\startupCache

I renamed startupCache.4.little (for safety) and relaunched Firefox. As I expected, Firefox recreated startupCache.4.little which is substantiated by a current timestamp.

However, the problem remains!

I don't know if startupCache.4.little is REALLY the right cache file, but I'm "shooting in the dark" at this point.

I have ChatZilla 0.9.92 installed and I did find a .93 version on the Internet. Do you think I should try that one?

Do you have any other ideas / suggestions?

I REALLY appreciate your help, so far!

Thanks!

Isn't chatzilla built into Seamonkey? It should be working on WinXP.

https://www.seamonkey-project.org/releases/2.49.5

Hi!

It looks like SeaMonkey may be the only way to solve this!

Because of the hardware limitations on the target machine (No SSE2), I was forced to install SeaMonkey 2.40 which is the last version that will run in a non-SSE2 environment.

The good news is that the "bundled version" of ChatZilla (0.9.92) within SeaMonkey DOES, in fact run! FINALLY!

HOWEVER, I want to be able to ADD a couple of networks to the list that shows up on the *client* tab. I was able to do this easily by editing the networks.txt file that was used by the ChatZilla add-in for Firefox that is no longer usable due to the aforementioned issue with the "certificate".

I can not locate this file for the bundled version of ChatZilla that comes with SeaMonkey 2.40. I need help finding the place where these networks are stored so I can edit the file. It is unlikely that it is named "networks.txt".

Thanks!

You could add a new server using fictional information, then search the profile for updated files.

Hi!

If I could figure out HOW to add a new server to the list that appears in the "bundled" version of ChatZilla I wouldn't need to "hand edit" the file. I could not find a place to do that, but I may just not have spotted it.

Thanks!