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Firefox opens and closes multiple SidebarUtil.tab on every startup

Open SUCM opened this issue 4 months ago • 6 comments

NoScript 13.0.8

every time I start Firefox (restores previous session&tabs), NoScript always open and close multiple SidebarUtil.tab. problem is NoScript always does SidebarUtil.tab randomly and sporadically, just not immediately. if I'm navigating and clicking when NoScript starts doing its tab flipping thing, Firefox shifts and moves the focus GUI/tab rows..etc to the SidebarUtil.tab causing me clicking on wrong things including closing tab or logout of website. if I want to avoid this, I have to start Firefox and not touch it for at least 30 seconds for NoScript to finish its business

now, a few questions

  • are these open & close SidebarUtil.tab on Firefox startup needed or bug? when I starts Firefox with no tab and manually open the tabs, none of the tab triggers NoScript to open&close SidebarUtil.tab
  • if SidebarUtil.tab are really needed, can SidebarUtil.tab be opened right next to the related tab so I can tell the targeted tab for the SidebarUtil.tab?

SUCM avatar Aug 09 '25 04:08 SUCM

Thanks for reporting.

are these open & close SidebarUtil.tab on Firefox startup needed or bug? when I starts Firefox with no tab and manually open the tabs, none of the tab triggers NoScript to open&close SidebarUtil.tab

In principle it's a bug, because it should not happen randomly on startup, but only when a web content page is navigated from the sidebar (typically one of the new Firefox AI chatbot integrations).

Also the tab stealing focus would be a bug, because it is explicitly created as an inactive (background) tab.

Some questions for you:

  1. Which Firefox version are you using?
  2. Have you got any special default layout, like a permanent sidebar or vertical tabs?
  3. Does the problem persist if you disable all your extensions except NoScript?

Thanks!

hackademix avatar Aug 09 '25 09:08 hackademix

  1. I saw this happening around Firefox 139.0.4 and persists all the way to the current latest 141.0.x
  2. I don't have any sidebar or vertical tabs. I have Tree Style Tab extension installed, but this still happens when I started Firefox with Tree Style Tab extension disabled
  3. disabling/enabling all extensions with exiting/starting firefox frequently in short time (minutes) seemed to have impact on this

additional notes

  • on shifting focus UI/tab. I have about 20-30 tabs restored on startup, so the horizontal tab bar always have scrollbar. NoScript always flips SidebarUtil.tab at the right most, which makes firefox shift focus and scroll tab bar to the right most opened SidebarUtil.tab tab then shift back to the original viewing tab. these shifting and moving UI while I'm clicking and/or pressing hotkeys are dangerous as mentioned before
  • the part I don't understand is why NoScript fires 4-6 SidebarUtil.tab after I started firefox with just 1 tab of Wikipedia page focused&opened while all other tabs are inactive/staled/waiting to be reloaded (only when I click on the tab). if I start firefox without Wikipedia page and wait for few minutes then opens a wikipedia page, NoScript doesn't fire any SidebarUtil.tab
  • the number of fired SidebarUtil.tab doesn't match number of restored tabs of any website, so I'm not able to figure out which website's restore tabs, if any, may be causing this
  • I had tried quickly select all restored tabs and reload them right on startup before NoScript starts the SidebarUtil.tab flipping, but NoScript didn't fire any SidebarUtil.tab. however, NoScript eventually started its SidebarUtil.tab flipping thing many seconds later

SUCM avatar Aug 09 '25 23:08 SUCM

when I start Firefox 141 with all extensions except NoScript disabled, NoScript still flips multiple SidebarUtil.tab on Firefox startup.

after few days of trying your ask#3, it looks like NoScript only flips SidebarUtil.tab on Firefox startup when the last Firefox exit was more than an hour before the current Firefox startup. that had caused confusion for me on whether enabled/disable extensions had any impact on this issue

SUCM avatar Aug 12 '25 11:08 SUCM

following the latest update to NoScript 13.0.9, I start noticing NoScript infrequently flipping 1 SidebarUtil.tab in the firefox private window (latest opened firefox window during that firefox usage) where I only have 4 wikipedia pages. these were more than an hour after firefox startup, but no new tab or website opened in the 25 minutes prior to the SidebarUtil.tab event. wonder if update or something else firefox itself does is triggering NoScript's SidebarUtil.tab flipping

SUCM avatar Aug 17 '25 22:08 SUCM

I don't use any sidebar, but I have an infrequent background tab popping in and out running this javascript. Actually while typing this just now. This is independent of private mode, and pretty much what is described in this issue

Currently on release version 13.0.9

AfromD avatar Sep 14 '25 18:09 AfromD

I am experiencing this issue myself. I have sidebar disabled in about:config, have all predictive and suggestions off everywhere in Firefox. When I open Firefox i get a dozen pages in my history of moz-extension://09ce5f06-dc72-4e84-bcea-cd6e12726d1a/nscl/service/SidebarUtil.tab.js. Why is any tab opening without my input and why is your extension looking for a sidebar that is disabled?

Robisagiant avatar Sep 26 '25 15:09 Robisagiant