Cookies shared across containers

[madduck]

Folks, I am pretty stumped having just hit by a case of cookies shared across containers in Firefox 144 and using Multi-Account Containers 8.3.6 (updated today).

Basically the issue is that if I open the same site in two containers side by side, and I change a cookie in one, the cookie is updated in the other as well, but not really always…

Here is a video to illustrate the problem: https://scratch.madduck.net/firefox-multiaccount-containers-leaking.webm

The two tabs are on the same URL in different containers, and logging into our ERP system on the left side only logs in the left side; The right side still has the login screen, even after reload. However, if I log in on the right side now, then the session ID obtained spills over to the left side, and both containers now have the same session with cookies synchronised across them. This feels wrong.

What's going on?

[emilio]

I think this is https://bugzilla.mozilla.org/show_bug.cgi?id=2006850 fwiw.

[madduck]

I think this is https://bugzilla.mozilla.org/show_bug.cgi?id=2006850 fwiw.

Thank you @emilio for filing that bug report!

[madduck]

This seems to be a display-only bug in devtools. Cookies are not shared. Devtools updates its display on cookie change without verifying that the container IDs match. Thanks Emilio for the triage!