The Directus Public role is what anonymous visitors get

Directus ships with a Public role that applies to requests carrying no credentials. Granting it read access to a collection makes that collection world-readable.

It is commonly granted while getting a front end working — the fastest way to make data appear — and then never revisited.

Settings → Roles & Permissions → Public. Review every collection with a read tick and remove the ones that are not meant for anonymous visitors.

For user-owned data, use an authenticated role with a permission filter on the owner field, so the query is scoped by the server rather than by your front end.

Request https://your-instance/items/<collection> with no Authorization header. A closed collection returns 403. Data coming back means the Public role still has read.

Leaving directus_users readable by the Public role. It exposes the email address of every account on the instance, which is a data breach even though no application data leaks.