alf.io is an open source ticket reservation system for conferences, trade shows, workshops, and meetups. An Improper Access Control issue in versions prior to 2.0-M5-2605 allows an organization owner to read system-level configuration secrets through organization/event scoped "single configuration" endpoints. The affected endpoints require organization or event ownership, but they accept an arbitrary configuration key and then return the first matching value from a lookup that includes system-level configuration. As a result, an organization owner can retrieve secrets intended to be administrator-only, including the system API key when it is configured. Version 2.0-M5-2605 fixes the issue.