SessionCookiesInternal.restore unconditionally uses SAMESITE_NONE as the sameSite flag. This is incorrect, the sameSite flag should have been saved at CookieStore.add and be restored later.

The effect of this is that after a session restore, session cookies could inadvertently be included in requests where they shouldn't have been included (when SameSite=Lax or SameSite=Strict).

The priority flag is not set for this bug.
:mikedeboer, could you have a look please?

For more information, please visit auto_nag documentation.

Sounds plausible to me, but I unfortunately don't have time to work on this right now. Please feel free to pick this up - I'd be more than happy to mentor!

Bug 1556151 - SessionStore: Save and restore cookie.sameSite flag

I just submitted a patch and added :mikedeboer as reviewer.

:mikedeboer, Could you assign this bug to me?

This is one of my first contributions to Firefox. Please let me know if there is anything I can improve on.

Pushed by dvarga@mozilla.com:
https://hg.mozilla.org/integration/autoland/rev/922be4adb708
SessionStore: Save and restore cookie.sameSite flag r=mikedeboer

https://hg.mozilla.org/mozilla-central/rev/922be4adb708

Dennis, well done for (one of) your first contribution(s) to Firefox! I'm looking forward to many more in the future!