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I agree, in my limited experience the sub remains consistent even when changing the Google Workspace domain. So the email changes but sub remains the same. The issue seems to be clients matching on email/hd claim instead.

I wonder what action is causing the sub to change like the author suggests is happening.

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At my current company, if an employee leave and come back, they'll keep the same OID in Entra but they'll get a new `sub` in Google workspace. We had to put in place a process to be able to use an internal tool that used the login with Google.

That's most likely dependant on how the IT department handled the deprovisioning/provisioning of users in our Google Workspace, I unfortunately don't have the details for that.

> I wonder what action is causing the sub to change like the author suggests is happening.

Indeed this would be very interesting.

This issue is also very similar to CVE-2024-25618.

What we did to mitigate this is the following: - Federated login with OIDC - Look for a user based on the sub claim - If they are found: authenticate that user and optionally update their profile (email, name, ...) based on then new id claims. - Else look for a user matching on the `email` claim and link the `sub` to that user - If no user is found create a new one

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