Existing users unable to log in and getting "422 The change you requested was rejected", with underlying error "Email is invalid"

Summary

We have a couple of reports for users unable to login to their existing accounts with confirmed email addresses, getting 422 The change you requested was rejected. When trying to reset their password, they get 1 error prohibited this user from being saved: Email is invalid.

Tickets (Internal Links):

• https://gitlab.zendesk.com/agent/tickets/523585
• https://gitlab.zendesk.com/agent/tickets/523487

Steps to reproduce

What is the current bug behavior?

Users should be able to login and reset their password

What is the expected correct behavior?

Users are unable to login or reset their password

Relevant logs and/or screenshots

• Kibana logs: https://log.gprd.gitlab.net/app/r/s/k1rve and https://log.gprd.gitlab.net/app/r/s/R4WNm
• The sentry record - https://new-sentry.gitlab.net/organizations/gitlab/issues/713555/events/052773090f6745378c75df90910f28fc/?project=3

Output of checks

This bug happens on GitLab.com

Possible fixes