As far as I know, this is not a native feature in Firefox. The only addon tracking that I can find is a history of recent updates. The only log files that I can find in Firefox are for errors with the sync feature.

Is there any way to look at Firefox's internal code?

The extensions.json file in the Profile folder does show the current state of installed extensions,as to whether they are enabled or disabled, but there is no date associated with that data.

Note that Stylish has been blocked by Mozilla because of abuse (Bug 1472948).

• https://blocked.cdn.mozilla.net/i1900.html
• https://support.mozilla.org/en-US/forums/contributors/713082

Yes, but I might have disabled it before, and I was wondering if there was any way to find out.

The status of installed extensions is stored in a file named extensions.json that is stored in your Firefox profile folder. If you make frequent backups of your system, you could look at older extensions.json files to see whether they show Stylish being enabled or disabled. (How to the look at the file is mentioned further down.)

Note: The May 23rd release, version 3.1.1, is the problem version. Before that, the Firefox extension shouldn't have been sending your history to the publisher, only the Chrome extension was doing that.

If you haven't made backups in the past six weeks, Windows 8.1 might have made some backups when it installed system updates. Do not use Windows System Restore!! But you can use a utility program to search inside shadow copies of your user data to try to locate an old file. Here are the steps:

(1) Set Windows to show hidden files and folders:

https://support.microsoft.com/en-us/help/14201/windows-show-hidden-files

(2) Download and run one of these programs:

• ShadowExplorer: http://www.shadowexplorer.com/
• System Restore Explorer: http://nicbedford.co.uk/software/systemrestoreexplorer/

Within the most recent restore points shown in the program, you can explore along this path to see whether you can find a recent shadow copy of your profile:

\Users\your-user-name\AppData\Roaming\Mozilla\Firefox\Profiles\

(3) Export the extensions.json file to a convenient location (not your live profile folder).

To view the extensions.json contents

Drag and drop the file onto a Firefox tab (to replace the existing page there). After a few moments, Firefox will show a structured view of the file and you can use Find (Ctrl+f) to jump to Stylish and check whether it was "active" (see screenshot) as of the date of the file.

I tried this but all I get are SyntaxErrors. Also, is there anything else I can look at?

JustToAskThisQuestion said

I tried this but all I get are SyntaxErrors.

Do you mean you found one or more old extensions.json files and dropped them onto a Firefox tab and Firefox said there was a problem with the file?

If Firefox won't display an extensions.json file, possibly it did not export well and is corrupted. You can view the code in a text editor, but it will be more difficult to read because it's all one long line (which hopefully will wrap).

It is still not working. Is there another file/s that I could look at?

JustToAskThisQuestion said

It is still not working. Is there another file/s that I could look at?

What do you mean by "not working"? What are you doing?

Looking at exensions.json files from different dates is the only method I can think of to see when an extension might have been enabled/disabled.

I keep getting SyntaxErrors or incomplete files.

Is there another way to see the release version?

JustToAskThisQuestion said

I keep getting SyntaxErrors or incomplete files.

Where do you get that? What is it that you are doing?

Is there another way to see the release version?

Well, if you are viewing an old restore point, you can look in the extensions folder to see the file, but that won't tell you the active/inactive status. The extension would be here:

[profilefolder]\extensions\{46551EC9-40F0-4e47-8E18-8E5CF550CFB8}.xpi

A .xpi file can be opened by a ZIP utility. If you export the file and change the file extension to .zip that will make it easier. Make sure Windows is set to display file extensions:

https://www.bleepingcomputer.com/tutorials/how-to-show-file-extensions-in-windows/

The manifest.json file will have the version number in it, for example:

"version": "3.1.1"

I get the errors by opening with Firefox. When opening with a text editor they seem empty or incomplete.

There also seems to be some trouble opening the xpi as a zip.

Okay, if the files are empty or incomplete, then the contents of the restore point from which you extracted them may be damaged. Sorry.

When opened in Firefox the files talk about a "bad control character" or "unexpected character". Is there any way to fix them?

Can you attach a screenshot?

• https://support.mozilla.org/en-US/kb/how-do-i-create-screenshot-my-problem
• use a compressed image type like PNG or JPG to save the screenshot

Here.

Click the Raw Data button and try using Find there. It will be harder to read, but hopefully you can track it down.

I couldn't find it there.

Does anyone know of any other options or files I can look at? Like the add-on's icon for example.

Is there a reason you're wanting to see if it was disabled before? While i understand what you want to do, I don't understand why. The add-on is blocked, and we recommend you use Styl-us instead. What's the difference if you disabled it before?