Wheels through 4.1.1 derives its default production error-email address from the Host header of the request that starts the application. If no explicit error-email recipient is configured, a mail server is configured, and the server accepts an attacker-chosen Host, an attacker whose request triggers a cold start can direct later error emails to an address under their control for that application's lifetime. Emails disclose error and request metadata; on engines/versions where scope dumps render, they may also disclose configuration secrets and other users' session/cookie data. On the Lucee 7 engine, scope dumps fail to render, limiting disclosure to header fields. This is fixed in 4.1.2.