Thunderbird 153: fresh profiles become partially unusable after some time; Settings and address autocomplete stop working

Automatically under extreme suspicion Kaspersky Endpoint Security

Removing prefs.js from an already affected profile did not restore the Settings window.

I would actually expect that to break a profile and loose most of the users settings as that is where they are stored along with all of their accounts. Even address book data becomes suspect as much of that database assignment and account assignment information is contained in the prefs.js as well.

As it is is corporate situation I would suggest restarting the device affected in safe mode with networking as you should have a wired network and see what affect that has. Also start Thunderbird in troubleshooting mode (hold the shift key while starting or restart from the help menu)

My guess the crippling affects of using Kaspersky will not be present and the whole thing will just function as it did in the past.

1. If that is not the case, open the error console on the affected device (ctrl+shift+J) Clear the console and report the errors that appear in the console when to settings windows is not displayed accessible editable. (right click makes copying them fairly simple)

2. Please post the troubleshooting information from the help menu (it has a handy copy button)

Please ensure that you antivirus/security solution is not attempting to manage Thunderbird through Group policies. There are templates that disable user access to settings.

As well as a number of other enterprise settings. See https://enterprise.thunderbird.net/manage-updates-policies-and-customization

Hence the request for the troubleshooting information. That should show most of those things if they are setup

Hello,

I have an important update regarding this issue.

Today, we received another affected laptop with the same Thunderbird problems. This time, I was able to investigate the issue **before modifying or rebuilding the Thunderbird profile**.

• • System information:**

- Thunderbird 153.5.0esr (64-bit) - Windows 10 Pro 22H2, build 19045.6456 - Kaspersky Endpoint Security installed

• • Symptoms observed:**

- The main Thunderbird application menu (☰) did not open. - Opening the Address Book displayed the Account Hub / Add Address Book screen instead of the existing address books. - Address autocomplete did not work when composing messages. - Some other settings pages remained accessible.

• • Diagnostic findings:**

1. The Error Console showed `NS_ERROR_NET_TIMEOUT` errors involving `CardDAVUtils.sys.mjs` and `RemoteAddressBookUtils.sys.mjs`. 2. No new relevant console errors appeared when clicking the nonfunctional menu button. 3. No Thunderbird policies were found under the HKLM or HKCU Mozilla Thunderbird policy registry keys. 4. No `distribution/policies.json` was present. 5. However, I discovered that Kaspersky had installed Thunderbird AutoConfig files (`kl_prefs_*.js` and `kl_config_*.cfg`), containing:

  `lockPref("security.enterprise_roots.enabled", true);`

  This confirms that Kaspersky modifies Thunderbird's configuration, but it does not prove that Kaspersky causes the issue.

• • Most important result:**

Following your recommendation, I booted Windows into **Safe Mode with Networking**.

Thunderbird worked correctly with the same previously affected profile:

- The application menu opened normally. - The Address Book worked. - Address autocomplete worked.

I then restarted Windows into normal mode.

• • Surprisingly, Thunderbird continued working correctly in normal Windows mode as well.**

I performed one additional normal Windows restart, and Thunderbird still worked correctly.

No Thunderbird profile files were manually repaired, replaced, or deleted during this investigation.

• • Important limitation:** I had not tried a normal Windows restart before entering Safe Mode. Therefore, I cannot determine whether Safe Mode itself resolved the issue or whether a normal restart would have been sufficient.

This result suggests that at least some of the profiles we previously considered corrupted may actually be affected by a temporary conflict involving the operating system, a background service, security software, or Thunderbird itself.

The laptop has now been returned to its user, and Thunderbird is currently working normally.

However, because similar failures have occurred repeatedly on multiple computers, I do not consider the underlying issue resolved.

• • Could you recommend what diagnostic information or logging we should collect if the problem occurs again, before restarting Windows?**

I would particularly appreciate advice on investigating possible interactions between Thunderbird and Kaspersky Endpoint Security.

Thank you for your assistance.

If I may offer a comment from the sideline. I defer to Matt 100% on all technical aspects, but my background was in corporate computing. You use Thunderbird as a production engine, not one for casual email. So, I recommend following a corporate approach:

1. ignore Mozilla recommendations to immediately apply all updates. Instead, pick a version and commit to it for a year with no updates. There are settings that allow disabling updates. You do not need new features and, if you are not experiencing any bugs, do not update.
2. each year, wait for latest ESR release to be in production for six months. At that point, install the new release on one pc and run with that for a month to ensure stability. Then, over one weekend, update all PCs.
3. Thunderbird is passive; it does not interfere with other processes. Kaspersky is intentionally invasive. Consider removing Kaspersky or conduct your own tests to stabilize its interaction with Thunderbird. You may well find that the embedded antivirus in Windows does the job satisfactorily.
4. Create backups of all PC profiles so can be readily reapplied. Creating new profiles always introduces risk.

Just my suggestions.