Insufficient Verification of Data Authenticity in the feedback function of Mesalvo MEONA (MEONA Client and MEONA Server). The MEONA Client transmits the recipient address of a feedback report to the MEONA Server, and the server sends the report to the transmitted address instead of the address configured on the server. The feedback function is available only in the MEONA administration area, which requires one of the administrative roles ADMINISTRATOR, SUPERADMINISTRATOR or TYPIST (catalogue editing), or the PHARMACIST role holding the PHARMACY_ADMINISTRATOR right, assigned explicitly by the operating hospital's administrators. Such a user who modifies the client request can cause the MEONA Server to send a message with content of the user's choosing, from the sender address configured on the server, to a recipient of the user's choosing, within the limits permitted by the operator's mail relay. The message can be used for social engineering because it appears to originate from an internal hospital system. Exploitation requires a MEONA account with one of the administrative roles named above and access to the operating hospital's internal network; MEONA is operated exclusively within closed hospital networks without exposure to the public Internet, and where a hospital permits remote access to that network at all, it is only through the hospital's own remote-access infrastructure (e.g. VPN) under the hospital's control. The message contains only the recipient, subject and text entered by the user; no data of other users or patients is disclosed. Mesalvo is not aware of any exploitation outside the reported security test. This issue affects MEONA Client and MEONA Server in versions 2024.10, 2025.04 (before 2025.04.24) and 2026.03 (before 2026.03.02). MEONA 2025.04.24 and 2026.03.02 (planned Q4 2026) enforce the configured recipient address on the server. Operators can restrict at their mail relay which recipients the MEONA sender address may reach.