A failure in the database connection is incorrectly interpreted as the software not being installed. This allows anonymous installer actions, such as `install/validate-site`, to be accessed on a production site if PHP is available but the MySQL endpoint is not. The process accepts a site name, serializes it via `Site::getName()`, and expands `${NAME}` expressions using `App::env()`. An unauthenticated attacker with a valid guest session cookie and CSRF token can provide a predictable variable name, such as `CRAFT SECURITY KEY`, to disclose sensitive information including process environment variables, `$ SERVER` entries, PHP constants, database credentials, or API keys. This issue requires an independent database outage to be exploitable.