How to crash Firefox; Instructions here; https://developer.mozilla.org/en-US/docs/Mozilla/How_to_report_a_hung_Firefox

Update: Note there is still an add-on that will safely & easily crash Firefox. Link (Thanks to Alice)

• Crash Me Now! (Simple) 1.0
  https://addons.mozilla.org/firefox/addon/crash-me-now-simple/

Using a terminal or a batch file is not too convenient, but I note the page Fred links to

• https://developer.mozilla.org/en-US/docs/Mozilla/How_to_report_a_hung_Firefox#Windows
  Includes a link to the executable crashkill.exe
  • https://ftp.mozilla.org/pub/mozilla.org/utilities/crashfirefox-intentionally/crashfirefox.exe <-- pastable but not clickable link - _{at least on Kitsune!}

It may be easier on Windows downloading that file and double clicking it to run it. It will crash Firefox reliably even if it has not yet hung. There was an add-on that could be used that was even easier but AFAIK it is not available or does not work on Releases now.

Another tip give Firefox at least 10 minutes to close down, if necessary trying from the Windows Task manager to close a hung Firefox. In many cases if Firefox hangs on closedown it triggers a timer and in due course that attempts to fire off a Crash Report. If you do try

TASKKILL  /IM  Firefox.exe  /T 

Either in a terminal or batch file may also be worth trying the /f option

TASKKILL  /IM  Firefox.exe  /T  /F

I am trying to not lose sight of the original question.

why does firefox keep downgrading

I can not think of any method Firefox itself has for downgrading. I suspect thirdparty software will be involved.&/OR you have multiple copies of Firefox installed. Could you for instance have an old ESR, a Portable, or 64bit version installed as well as the Release ?

Please search the whole computer for all files firefox.exe Search from Drive (C:) and use kind=program option to speed up the search.It may take quite a few minutes to complete.It may pick up a few similar names such as firefox installers but ordinary users with standard installs will only have the one actual file named "firefox.exe"

FredMcD said

Let's try this. Create a Windows Batch program. Let's call it: KillFirefox.BAT It may create a crash. I don't know.

That half worked. It does kill FF. It does create a crash report.

  bp-636789fa-f0b6-4abb-ad1b-b62702161110

But it doesn't cause it to revert to v45.

So that's promising. We'll see what happens next time it locks up. If nothing else, I have an alternate way to kill it that may not revert.

crashfirefox.exe has the same affect.

It does kill FF. It does create a crash report.

 bp-77b40a4d-22c7-41f4-998d-a37a22161110

But it doesn't cause it to revert to v45.

Thanks for all the ideas, Brad.

As far as searching C:

Yes, all my executables are on C: No, searching didn't find anything besides the installers and the copies I made when backing up the Mozilla Firefox folder.

Note, the executables in those folders are v45. They were actually downgraded. It's not finding some other exe on the disk somewhere.

At this point, I'm going to let this go until it happens again.

Thanks again, Brad.

bp-636789fa-f0b6-4abb-ad1b-b62702161110 Version 49.0.2

Signature: IPCError-browser | ShutDownKill

Attention Sumo's there are 30 related bug reports ++++++++++++++++++++++++++++++++++++++++ bp-77b40a4d-22c7-41f4-998d-a37a22161110 Version 49.0.2

Signature: @0x0 | __RtlUserThreadStart | _RtlUserThreadStart

Attention Sumo's there are 6 related bug reports

msmpeg2vdec.dll = Microsoft DTV-DVD Video Decoder

Why do you have Fx45 installers or executables in the first place ?

I guess you will say because Firefox downgraded and installed them, but I an not aware of any way in which Firefox ordinarily does that so you can just remove them. take care that you are removing installers or executables and not profiles.Hopefully that will stop the downgrading issue.

John99 said

Why do you have Fx45 installers or executables in the first place ? I guess you will say because Firefox downgraded and installed them, but I an not aware of any way in which Firefox ordinarily does that so you can just remove them. take care that you are removing installers or executables and not profiles.Hopefully that will stop the downgrading issue.

About the v45 exe:

I had one FF folder, properly upgraded to v49. Something happened and FF was somehow downgraded to v45. I renamed the folder, reinstalled. Now I have a Mozilla.OLD and a new Mozilla. The v45 exe is left as an artifact in OLD.

About the v45 installer:

I didn't notice any 45 installers in the download folder resulting from the search the other day, but I wasn't looking for them. I was only looking for other exe's. I will review installers on Monday.

I only see 'Firefox Setup Stub 49.0.2.exe' installers in the downloads folder. No v45 installers in sight.

Could you try this for the downgrading issue?

• Go to C:\Users\<username>\AppData\Local\Mozilla\updates\
• Try moving all content elsewhere
• Update when asked and restart
• Wait for the issue to reoccur

In the moved content including subfolders, there may be .log files offering more info, although I don’t think they will tell you what went wrong.

The crashes may have another reason.

Also see this page.

Thanks for the reply. It sounded promising.

'Updates' contained only an empty randomly named folder. No logs, no content.

Moved folder to Updates.OLD

Well… The above seems like a good sign, as long as there is no pending update. Yet I would expect to see 2 files in each folder (see next), not empty folders only. Was this the case when 49.0.2 was installed, or after rolling back to 45?

Some more thoughts:

• In addition to the C:\Users\<username>\AppData\Local\Mozilla\Firefox\Mozilla location given above, also look at/in C:\Users\<username>\AppData\Local\Mozilla\Firefox\Mozilla Firefox and C:\Users\<username>\AppData\Local\Mozilla\updates.

In fact, do a full scan on your C drive (or even all drives) for files "active-update.xml", "updates.xml", and the "updates" folder. The fact there is no updates.xml and active-update.xml when you searched also makes me wonder why, as I *think* both files should be there for each randomly named folder. Such a folder belongs to each Firefox copy on your system (rather: release/beta/aurora, not version numbers) and the associated profile(s) last used with it, and should be stored in the browser.taskbar.lastgroupid preference in prefs.js. (I also found that string twice in my registry, so you might want to check that to find more, in particular on obscure spots.) Ideally and when only one Firefox copy is installed, you should see it once in the profile's prefs.js, and have one folder named that way. The point is that an empty randomly named folder most likely belongs to a Firefox copy that does not or does no longer exist. Hence, the number of as well as date stamps for those folders and files should indicate something and make sense.

• If you find any of these files and folders with a search, move them elsewhere (More info). Also, open each active-update.xml file using a text editor and make sure they only contain one line - I think their file sizes should be 57 bytes only. The updates.xml files contain the update history and may vary in size. This should be true with no updates pending, but I don't think there ever was - you seem to be "downgraded" after crashes only (which is suspicous). Did you ever see Firefox actively perform an update anyway? You should either see a dialog telling Firefox is installing your updates and will start in a few moments…, or the About dialog displaying an update is in progress, even requiring you to click "Restart now to complete installation". This is just to be sure it is about a valid update and not just some other copy starting or performing some unofficial update.
• When Firefox crashes, don’t restart it yet to prevent it to "downgrade" to 45, but scan your disk at this particular point to see if those files and folders above exist anywhere (else?).
• What does the Update History log in Firefox say? See Options > Advanced > Update > Show update History. It should contain all "legitimate" updates, though they may be empty after deleting/moving the updates.xml files above. Of course we're curious to see if it contains valid downgrade and upgrade entries.
• What happens if you force a manual update when on 49 in Help > About Firefox?
• How many profiles do you have? Are you sure both instances start using the same profile? Have you tried creating and switching to a new profile?
• Are your plugins up-to-date? Do a plugin check here.
• Is there any chance you clicked some update offering a file called firefox-update.js recently?
• Can you check for any software or its features mentioned here? Also, please read the rest of the page.
• Although I think that you have proven the Firefox program files truly get modified by looking at the Program Files\Mozilla Firefox folder's content after Firefox downgraded, I would like to be sure about the firefox.exe process running, both in "normal" mode (49.02, or 50.0 that has come out meanwhile) and the one when running 45.
  1. Start up Windows Task Manager and look at the firefox.exe process in the Processes tab. There should be one active for v45, maybe more for 49 (if e10s is enabled, not sure).
  2. Right-click the entry and select "Open file location". You should end up in the real installation folder. Do they match when running 45 and 49?
  3. Additionally, the updater.exe process (residing in the Firefox program files folder) should be running during an update.
• If I read well, you haven’t run a registry scanner yet. I suggest you do. Better perhaps, run a malware scan, or even a virus scan.

I’m out of ideas at this point, but my thoughts are your system could be affected by some piece of malware (or worse) trying to trick you into silently downgrading Firefox and then abusing some known vulnerability, either by a vulnerable plug-in or in some other way, but by intentionally making it crash and downgrade to 45 using a hidden file on disk, or by downloading it before it starts (which doesn't look that way.)

Wow, thanks for all the time and attention you put into this.

> Was this the case when 49.0.2 was installed, or after rolling back to 45? I only backed up the directory in "Program Files", so I can't tell.

Most of these I'll have to check when I'm back in front of that computer.

> When Firefox crashes, don’t restart it yet to prevent it to "downgrade" to 45, Good point. I don't know if the downgrade happens when it crashes or when it starts back up. BTW, the files were very well marked and easy to distinguish versions. Thanks for that.

> What happens if you force a manual update when on 49 in Help > About Firefox? That is what I've been doing. It works great.

> Are you sure both instances start using the same profile? They both come up with the same pages open. I don't know if that proves anything.

> Have you tried creating and switching to a new profile? No.

> Did you ever see Firefox actively perform an update anyway? You should either see a dialog telling Firefox is installing your updates and will start in a few moments…, I've *never* seen this for the downgrade. Only for the upgrade. That's what clued me in that there was an issue. That it kept upgrading to the same version. About clearly says what version it is on, and if not 49, offers an upgrade, as expected.

A couple of thoughts

updates.xml It may be worth making copies of updates.xml files and noting that Firefox itself is capable of opening & reading such files. They give more detailed info about your updates than what is ordinarily seen. Just possible they may offer some sort of clue as to what is happening.

about:profiles

Key that in to the address bar and press enter. I do not think that is a fully functional feature yet but it does list your profiles, and show which one is in use. On Fx 45 you will need to use about:support and then look for the button to open the profile location to find which profile is being used.

Only shows the default profile.

Update: Note there is still an add-on that will safely & easily crash Firefox. Link (Thanks to Alice)

• Crash Me Now! (Simple) 1.0
  https://addons.mozilla.org/firefox/addon/crash-me-now-simple/

John99 said

....
It may be easier on Windows downloading that file and double clicking it to run it. It will crash Firefox reliably even if it has not yet hung. There was an add-on that could be used that was even easier but AFAIK it is not available or does not work on Releases now.

Another tip give Firefox at least 10 minutes to close down, if necessary trying from the Windows Task manager to close a hung Firefox. In many cases if Firefox hangs on closedown it triggers a timer and in due course that attempts to fire off a Crash Report. .....

John99 said

Crash Me Now! (Simple) 1.0

Looks good. But if Firefox is locked up/frozen, you still need something else.

John99 said

Note there is still an add-on that will safely & easily crash Firefox. Link (Thanks to Alice)

That looks useful. In this case, we were successful at crashing FF. But it didn't reproduce the downgrade behaviour. When it does lock up, it eventually brings up a dialog that suggests restarting it. If it comes up again, I'll let it go longer to get the crash report. It is after this dialog that it reliably downgrades.

But, it has been more than a week since the last crash. The difference was reinstalling from scratch instead of upgrading. Before that it was crashing, on average, more than once per day.

Thanks, Brad.

> > > 'Updates' contained only an empty randomly named folder. No logs, no content. > > Was this the case when 49.0.2 was installed, or after rolling back to 45? > I only backed up the directory in "Program Files", so I can't tell.

OK, I was aiming at the update files above (=active-update.xml and contents of the update/0 folder), intended to know if there were files pending prior to the downgrade - or at least after or even before the crash. _{Nit: I used the word "stalled" twice in my previous message where "pending" was intended (just edited it) so this may have been confusing. Not native… ;)}

> > What happens if you force a manual update when on 49 in Help > About Firefox? > That is what I've been doing. It works great.

Yes, but what happens when Firefox is on 49?? It should not offer one then, OR it should offer the 45 downgrade too if it would be a valid upgrade. I would not expect an automatic downgrade notification.

> > Are you sure both instances start using the same profile? > They both come up with the same pages open. I don't know if that proves anything. Yes, most likely. As John wrote, you could see the number of profiles by about:profiles (they should match the number of profile folders.) As of Firefox 50, you can create new profiles, as well as start other profiles from within the current session. However, I only asked because of expected behavior, not to fix or avoid the problem, and don’t think the crash/downgrade is related to a profile related setting. And if there was, better use the same profile for now to avoid that.

> I've *never* seen this for the downgrade. That’s not really a surprise, and what I was hoping for.

Another thing is, I don’t think Firefox is even capable of or allowed to do a downgrade (as John wrote), at least not using the update mechanism, unless it would think it’s 44 or less, which isn’t likely at all. To me it’s most obvious something is trying to trick you by forcing a crash first (maybe at random times), followed by some file replacement other than by using the folders and files described. Hence I expect the updates.xml to only contain info about 45 -> 49 updates, and you may not find any pending update file right after it crashed. That would haven been great and could have pointed you to its location, but if that’s the way it worked, it would have caused Firefox to update in a visible way. Sidenote: I just found a similar question that unfortunatley has no answers, but note the program files location there. There is another unanswered one here. I’d say they point to rare hijack attempts. Did you run any scans yet?

New thought: I never tried, but you might be able to set Firefox’s program folder to Read-only, so any write attempt may cause an error message pointing to the responsible process.

(Fred/John:) What is your intention of forcing a crash? Is it to see if that triggers a downgrade afterwards? Or just to see the crash report and do a comparison?

Tonnes said

(Fred/John:) What is your intention of forcing a crash? Is it to see if that triggers a downgrade afterwards? Or just to see the crash report and do a comparison?

I just added the update comment for information. The addons are the most user friendly method of triggering crashes, and the addon I used to use is not signed. Most users do not like using commands / bat files. (I am familiar with good old fashioned DOS but am clueless on the newfangled PowerShell )

We do now know from Brad's replies that forcing a crash not trigger a downgrade.

Yes both points with trying to force a crash

If hangs are a problem it gives information that may help with the hang. It also unambiguously identifies the Firefox version in use at the time of the crash.

I also wondered if the crash or the recovery from it would trigger the downgrade and if so it would also on the next crash again confirm the Firefox version. It would also rule out the possibility that all that was changing is the User Agent string &|or the profile.

New thought: I never tried, but you might be able to set Firefox’s program folder to Read-only, so any write attempt may cause an error message pointing to the responsible process.

In my Windows 10 install of Fx Release 32 bit the Mozilla Program folder content is already read only for the standard user. Curious I have never tried that. I guess changing the whole folder to Read & Execute for all is safe so I will try it. (I will need to revert for any updates - and look out for error messages)