The correct option is Create an organization secret and restrict it to selected repositories using a policy.

An organization secret lives at the organization level and can be scoped to selected repositories so you define the password once and only the six internal repositories can read it. This follows least privilege and gives centralized management for rotation and auditing. As an organization owner you can grant and revoke repository access to the organization secret without touching each repository.

Create a repository environment secret in every repository and control access with required reviewers is not the most secure or manageable choice because environment secrets exist only within a single repository. This forces duplication of the same secret across six repositories which increases exposure and complicates rotation, and required reviewers approve deployments rather than providing centralized secret governance.

Store the password in each workflow file to keep configuration simple is insecure because secrets must never be committed to source control. They would be exposed in repository history and forks and would be difficult to rotate safely.

Google Secret Manager is not the best answer for this question because it asks how an organization owner should define the secret in GitHub so that only selected repositories can access it. While external managers can be integrated with additional configuration, that approach is not a native GitHub control that cleanly scopes access to specific repositories inside the organization.

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