Slack and Firefox multi-container account in conflict
March 1, 2021 5:42 PM   Subscribe

My work Slack account suddenly won't open in my Firefox work container after having no problems doing so for the past few months.

I installed the Firefox Multi-container add-on. Everything with it has been fine until today. I have a number of containers (personal, work, etc.). I tend to leave my tabs open and my containers sorted by grouping. One of the containers that's always open in my work group is Slack for browsers, and it is signed in to my employer's Slack account.

Today, when I fired up the computer (I power it down at nights) and launched the browser (FF 86.0) Slack wouldn't open at all. I tried refreshing. I tried closing the tab and reopening a new one, and nothing. I've got a completely white screen. (I do have the Slack app and resorted to that, but it's not my preference for everyday activities.)

Tonight, I decided to play around a bit to figure out what the problem was. It turns out I can make Slack load in my browser, as long as it's in a completely different (i.e. non-work) Multi-container grouping. Right now, for example, it's loaded in my "personal" grouping.

As far as I know, I did nothing to block it from loading in the work group, but it's computer, so something could have happened in the background.

The questions are what do I need to check and how do I get Slack working again in the work group?
posted by sardonyx to Computers & Internet (3 answers total)
Best answer: Have you tried deleting all Slack cookies? There is a user friendly UI for this in Preferences which is worth a try (Cookies > Manage Data > search for "slack" > Remove All Show).

If that doesn't work you might need to get out the big guns: go to your Slack URL. You'll presumably get the white screen. Hit Cmd-Alt-I (upper case i) to open the console. Choose the "Storage" tab. Then go through Cache, Cookies, Indexed DB, Local Storage and Session Storage and delete everything under Then close the tab and try again. You'll need to log in again if this works.
posted by caek at 9:00 PM on March 1, 2021

This problem can happen if your company uses Microsoft Single Sign-On (SSO) to log you into Slack.

The reason is that Firefox does not support device authentication, which means that Microsoft's conditional access policies won't work on Firefox. If you can log into your work Slack on Chrome or Edge, it's likely this is the problem, and there is nothing you can do about it.

(This may not be the problem at all, and a complete red herring. But IF your employer uses Microsoft SSO with conditional access policies, it won't work on Firefox. I know this because I have seen, investigated, and closed several support tickets from users who suddenly got a totally white screen in Firefox when using Slack, once Microsoft SSO with conditional access policies was turned on.)
posted by underclocked at 9:51 AM on March 2, 2021 [1 favorite]

Response by poster: Thanks for the suggestion, caek. That work. I now have Slack open in a work tab instead of a personal one, which will help keep me organized.
posted by sardonyx at 2:20 PM on March 2, 2021

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