OpenReception's appointment booking software provides an end-to-end encrypted appointment booking platform. Prior to version 1.0.4, the route `POST /api/tenants/{tenantId}/staff/{staffId}/crypto` accepts and stores attacker-controlled ML-KEM-768 public keys against any tenant on the platform without authentication. The handler logs an "Unauthorized crypto key storage attempt" warning when neither a session nor a registration cookie is present, then proceeds to insert the row regardless. The platform's E2E claim that "even administrators cannot view sensitive information" is broken: any unauthenticated network attacker can register themselves as an additional encryption recipient for any tenant's future patient appointments. A second variant of the bug suppresses the unauthorized-warning log entry. The Zod schema makes the `email` field optional. When the request body omits `email` and the request carries no registration cookie, the comparison `registrationEmail === email` becomes `undefined === undefined`, which evaluates to `true`. The handler treats the request as a legitimate registration flow, skips the warning entirely, and stores the row. Successful storage is still recorded as an `[info]` log line, but the security-relevant warning that operators are most likely to monitor or alert on is gone. The `staff_crypto` table has no unique constraint on `user_id`, so an arbitrary number of attacker rows can coexist for the same staff identifier and all return as `is_active=true`. The supplied `staffId` does not need to match any existing user or pending invite. Schema validation on `passkeyId`, `publicKey`, and `privateKeyShare` is also weak: the literal string `<placeholder-base64>` was accepted, indicating no length, format, or cryptographic-validity check beyond field presence. This weakness is independent of the auth bypass but compounds it: a poisoned directory can also be filled with malformed entries that break legitimate booking flows. The injected key is consumed by the public booking flow. After completing the unauthenticated `bootstrap-challenge` and `bootstrap-verify` ceremony as a "patient", the resulting `bookingAccessToken` is accepted by `GET /api/tenants/{id}/appointments/staff-public-keys`, which returns the attacker-controlled keys alongside any legitimate ones. A new appointment encrypts its tunnel key with ML-KEM to all listed recipients, so the attacker becomes a co-recipient of the encryption and can decapsulate the tunnel key with the matching secret. From there, all appointment payloads for that booking are decryptable. Version 1.0.4 patches the issue.