Affected versions

• Firefox 77.0a1

Affected platforms

• Windows 10 x64
• macOS 10.15

Steps to reproduce

1. Reach about:preferences#privacy and Set the Custom option:
   • Tracking Content - In all windows
   • Cookies - All third-party cookies (may cause websites to break)
2. Reach https://senglehardt.com/test/identity_providers/google.html and Click the Sign in Prompt.
3. Provide a valid email address and a password then sign in.

Expected result

• The google button string remains unchanged "Sign in".

Actual result

• The google button string is changed to "Signed in".

Regression range

• This is a recent regression, because I can't reproduce the issue on Firefox 76.0.

I can't reproduce this on the latest Nightly 78.0a1. Maybe this was fixed. Could you check again with the latest Nightly?

I can still reproduce the issue using Nightly 78.0a1 (2020-05-05) on Windows 10 x64.

Hi, I was able to get a regression window for this issue and it seems Bug 1625568 might be the cause of it. Here is the First and last known good builds:

First known BAD:

https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=30fe730b5ab1a63d516ac7edcebf26e19c598f1a&tochange=07f22519f90f41b59bfd5b2b10e9c5ac2fb537e3

Last known GOOD:

https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=1034c92fd11898d8ae595f8cb7518d641c299dcc&tochange=07f22519f90f41b59bfd5b2b10e9c5ac2fb537e3

The regression window points to code that landed in 76 but the comment #0 says that 76 is not affected. Is it a nightly-only regression?

Oh great, I figured out what's going on here. Right now, we've enabled the heuristic for rejecting third-party cookies in Nightly. So, the third-party cookies would be accessible in this test case since the heuristic will be triggered. So, "Signed in" is expected here in Nightly, but only in Nightly.

The good news is that this heuristic is put behind a pref "network.cookie.rejectForeignWithExceptions.enabled". Could you turn this pref off and try it again?

With this pref network.cookie.rejectForeignWithExceptions.enabled set to false i was unable to reproduce this issue at all.

Thanks, marking as disabled for beta and release.

This behavior is expected in Nightly. And we can resolve this issue by turn the pref "network.cookie.rejectForeignWithExceptions.enabled" off. Resolve this as WFM.

Sorry, Resolve Invalid is more appropriate.