User allowed to create an account with the same email in the same instance even though user already exist in "Portal on Customers" list

Summary

This issue happen when Customer Portal and JIRA instance is set to public. At first, user created an account in Customer Portal. Then, they try to create an account with the same email when browsing the JIRA instance. This will create an Atlassian Account. Due to this, the user will have two account with same email but different username.

Environment

Cloud

Steps to Reproduce

1. Ensure your email address is not currently associated to an Atlassian ID
2. Browse to a Service Desk Portal that is open to public sign up
3. Sign up for a customer account with your email address
4. Log out of your new portal user account
5. Browse to the non-portal homepage of the same Jira instance that has public sign up enabled
6. Sign up for an Atlassian ID using the email address used to create a customer user earlier via the login/signup screen for the instance

Expected Results

During user creation it should check if the account already existed in "Portal only customer" list.

Actual Results

Duplicate user account created.

Notes

(Optional - If Necessary)

Workaround

1. Browse to Jira Administration → User Management → Jira Service Desk → Portal Only Customers
2. Search for the duplicated user
3. Press the Migrate to Atlassian account button
4. The portal only user will now be removed, their issues will be reassigned to their new Atlassian ID Jira account.