Hi

Which add-ons do you have installed in Firefox?

If you open the extensions folder in your Firefox profile? If there a folder or file there with a filename equivalent to the error message you are seeing?

Oops, small mistake. I had several windows open and got confused. Sorry.

I posted the question using Firefox v91.0.2 but the message only appears when using v54 (my default).

Application Basics

Name: Firefox Version: 54.0.1 Build ID: 20170628075643 Update Channel: release User Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:54.0) Gecko/20100101 Firefox/54.0 OS: Windows_NT 10.0 Multiprocess Windows: 0/2 (Disabled by add-ons) Google Key: Found Mozilla Location Service Key: Found Safe Mode: false

Crash Reports for the Last 3 Days

This application has not been configured to display crash reports.

Extensions

Name: Add to Search Bar Version: 2.9 Enabled: true ID: add-to-searchbox@maltekraus.de

Name: Add-ons Manager Context Menu Version: 0.4.2.1-signed.1-signed Enabled: true ID: amcontextmenu@loucypher

Name: Addons Manager Hilite Version: 3.0 Enabled: true ID: addonsmgrhilte@cfl

Name: Application Update Service Helper Version: 2.0 Enabled: true ID: aushelper@mozilla.org

Name: Autofill Version: 3.5.1-signed.1-signed Enabled: true ID: firefox-autofill@googlegroups.com

Name: Back to Top Version: 8.0.1-signed.1-signed Enabled: true ID: {3C9A65A6-9563-4485-BA4A-4BCD698BCFB4}

Name: BehindTheOverlay Version: 0.1.1.1-signed.1-signed Enabled: true ID: jid1-Y3WfE7td45aWDw@jetpack

Name: Case Changer Version: 2.0.0.18.1-signed.1-signed Enabled: true ID: casechanger@plugin

Name: Classic Theme Restorer Version: 1.6.4 Enabled: true ID: ClassicThemeRestorer@ArisT2Noia4dev

Name: Close Tab By Double Click Version: 1.14.1-signed.1-signed Enabled: true ID: close@doubleclick

Name: Context Search Version: 0.6.4 Enabled: true ID: {902D2C4A-457A-4EF9-AD43-7014562929FF}

Name: Copy As Plain Text Version: 1.0.9.1-signed Enabled: true ID: {1a5dabbd-0e74-41da-b532-a364bb552cab}

Name: Dictionary Extension Version: 3.0.12.1.1-signed.1-signed Enabled: true ID: jid0-raWjElI57dRa4jx9CCiYm5qZUQU@jetpack

Name: Disable HTML5 Autoplay Version: 2017.8.20 Enabled: true ID: disable-html5-autoplay@afnankhan

Name: disallow Script Button Version: 0.3.3.1-signed.1-signed Enabled: true ID: disallowscriptbtn@code.google.com

Name: Download Status Bar Version: 15.0.0.1 Enabled: true ID: {6c28e999-e900-4635-a39d-b1ec90ba0c0f}

Name: FEBE Version: 8.9 Enabled: true ID: {4BBDD651-70CF-4821-84F8-2B918CF89CA3}

Name: Firefox Screenshots Version: 6.6.0 Enabled: true ID: screenshots@mozilla.org

Name: Forecastfox (fix version) Version: 2.4.8 Enabled: true ID: forecastfox@s3_fix_version

Name: Free Download Manager Version: 3.0.55 Enabled: true ID: fdm_ffext2@freedownloadmanager.org

Name: Grammarly for Firefox Version: 8.857.0 Enabled: true ID: 87677a2c52b84ad3a151a4a72f5bd3c4@jetpack

Name: Link Toggler Version: 0.3.1-signed.1-signed Enabled: true ID: {CFC31648-F870-11DF-80F3-9B4EDFD72085}

Name: MClickFocusTab Version: 7.0.20111026.1-signed.1-signed Enabled: true ID: mclickfocustab@moztw.org

Name: Multi-process staged rollout Version: 1.50 Enabled: true ID: e10srollout@mozilla.org

Name: Multirow Bookmarks Toolbar Plus Version: 1.9 Enabled: true ID: {4c7097f7-08f2-4ef2-9b9f-f95fa4cbb064}

Name: NoSquint Plus Version: 50.0 Enabled: true ID: zoomlevelplus@zoomlevelplus.net

Name: Open in Google™ Translate Version: 0.1.2 Enabled: true ID: jid1-r2tWDbSkq8AZK1@jetpack

Name: Open in IE Version: 1.5.0.1-signed Enabled: true ID: openinie@wittersworld.com

Name: OPIE Version: 6.6 Enabled: true ID: OPIE@guid.customsoftwareconsult.com

Name: Password Exporter Version: 1.3.4 Enabled: true ID: {B17C1C5A-04B1-11DB-9804-B622A1EF5492}

Name: Pocket Version: 1.0.5 Enabled: true ID: firefox@getpocket.com

Name: ProgressMeter Version: 1.2.1-signed.1-signed Enabled: true ID: progress-meter@bgoluboff.org

Name: Quit Firefox Version: 0.2.1-signed.1-signed Enabled: true ID: {22f6d978-67ce-4738-9201-d22df1c32896}

Name: Restart Version: 3.0.2 Enabled: true ID: Restart@schuzak.jp

Name: Rights To Close Version: 1.0.4.1-signed.1-signed Enabled: true ID: shan.developer@gmail.com

Name: Saved Password Editor Version: 2.9.6 Enabled: true ID: savedpasswordeditor@daniel.dawson

Name: SearchThisSite Version: 0.37.1-signed.1-signed Enabled: true ID: {c71ff04d-f001-1fc1-1fc1-c71ff04df002}

Name: Send Tab URLs Version: 2.3 Enabled: true ID: {4aebcd37-f454-4928-9233-174a026ed367}

Name: Space Next Version: 0.34.1-signed.1-signed Enabled: true ID: {c71ff04d-f001-1fc1-1fc1-c71ff04df005}

Name: Thumbnail Zoom Plus Version: 4.2 Enabled: true ID: thumbnailZoom@dadler.github.com

Name: uBlock Origin Version: 1.9.8 Enabled: true ID: uBlock0@raymondhill.net

Name: Undo Closed Tabs Button Version: 4.0.1 Enabled: true ID: undoclosedtabsbutton@supernova00.biz

Name: Vertical Toolbar Version: 1.0.17 Enabled: true ID: verticaltoolbar@xuldev.org

Name: Video DownloadHelper Version: 6.3.3 Enabled: true ID: {b9db16a4-6edc-47ec-a1f4-b86292ed211d}

Name: Web Compat Version: 1.1 Enabled: true ID: webcompat@mozilla.org

You can search the about:debugging page (This Firefox) to see if you can link this UUID to a specific extension.

Okay, thank you.

Given that this is not happening in 91 (the current ESR version) and is in 54 (which I think was the ESR version before last), I guess there is a choice to make. If you are planning to update, and do not need this looked into, happy to do so.

If you do want this looked into further, I can install a copy of 54 and the not-so-big-name add-ons and see if I can narrow down which one is causing this. This could be a big job considering that the add-ons may have have been updated and the number of add-ons you have installed.

Unfortunately, support volunteers cannot determine which extension that is, because Firefox assigns each extension a randomly generated Internal UUID and that is what is used in the URL of the content script (as discovered by that site).

You can search the about:debugging page (This Firefox) to see if you can link this UUID to a specific extension.

The information is on the "This Firefox" panel -- you can paste this to the address bar and press Enter to load that page:

about:debugging#/runtime/this-firefox

Then use Find in page (Ctrl+F) to find part of the UUID (for example, 658f8192). Assuming it is listed -- disabled extensions are omitted -- you should be able to determine which extension has that "Internal UUID".

Is this something I need to worry about?

I guess we'll find out!

You can search the about:debugging page (This Firefox) to see if you can link this UUID to a specific extension.

I gave it a try, but the information was confusing. Also, it would have taken several days.

I tried the old standby, Troubleshoot(Safe) Mode. The message was gone, so I disabled the add-ons a group at a time.

It turned out to be; Name: Disable HTML5 Autoplay Version: 2017.8.20 ID: disable-html5-autoplay@afnankhan

I guess it makes sense. Thank you everyone for your help on this.