Firefox Immediately Crashes

Hi did you uninstall via the Windows GUI or manually do something, and after uninstall did you [Restart] Windows before installing again?

Another question how did you reinstall?

https://www.firefox.com/en-GB/download/windows/

Yes I uninstalled with the Windows, settings, apps, installed apps. Yes I restarted the computer. Yes I reinstalled from the Firefox website for windows. Upon reinstall Firefox works. However, once closing it, when you try opening it again it immediately crashes and the Firefox Crash Reporter window appears.

Would these be captured in the crash reporter?

1. Enter about:crashes in the Firefox address bar and press Enter. A list of Submitted (and Unsubmitted, if any) Crash Reports will appear, similar to the one shown below.
2. Copy the 5 most recent Submitted Report IDs that start with bp- and then go back to your forum question and paste those IDs into the "Post a Reply" box.

Note: If a recent Report ID does not start with bp- click on it to submit the report.

(Please don't take a screenshot of your crashes, just copy and paste the IDs. The below image is just an example of what your Firefox screen should look like.)

More information and further troubleshooting steps can be found in the Troubleshoot Firefox crashes (closing or quitting unexpectedly) article.

It is not possible to put something into the Firefox address bar because it immediately crashes. I copied and pasted the info from the crash reporter into a text document, but I don't see a way to attach a file to this message, and it's to long to post in this message.

There is just one file in the crash report folder, which is:

bp-30861f28-0e01-47b9-b5db-468f30260903

Thanks.

That's a hard crash on most likely security grounds. So it's possible something you have added in your profile during that browsing session is triggering it. An addon trying something perhaps, something tweaking some browser internals, or even a content page doing some shenanigans across origins…

If you start with a new profile (if you can't launch the normal way: Win + R › firefox.exe -P) and make a new profile there, and don't add anything extra to it — does that testing profile work between restarts?

Yes I tried that and the testing profile works ok. What should I do to fix the issue when signing back in? Delete add-ons?

So apparently something is trying to load a local file:

  Illegal load attempt of file: URL from webIsolated

… like an iframe trying cross–origin navigation to your local files or something. Can't tell if that comes from extensions, or your former tabs (if you use session restore on launch) — however I'm not sure that would only exhibit if relaunched and not while browsing, that's a weird timing. I'd more suspect some addon doing something weird.

It would help understanding this better as it's related to a security finding mozilla.org/security/advisories/mfsa2026-84/#CVE-2026-84143 and being investigated in bugzil.la/2066354#c3

My homepage is a local file. Does firefox no longer support that?

It does support it just fine. Apparently during the restore an addon might be trying to do something with it, and/or there are iframes from different origins involved or something. If you just set your local html homepage in the new profile, without any addons etc., does it still work? If you can break the profile just with your html and nothing else, that would be really interesting to look into.

If I create a new profile and just set my local file as the homepage it does work ok. The problem is when I sign into my Firefox account then it starts crashing again. It is also doing the same thing on my Mac computer now too. I guess I won't be using it anymore since it doesn't work and won't sync between computers.

Could you share the details in https://bugzil.la/2066354 as it sounds pretty important to understand, thanks!