MariaDB Connector/J is used to connect applications developed in Java to MariaDB and MySQL databases. From 3.0.0 until 3.3.7, 3.4.5, and 3.5.11, the connector assumed result bytes were UTF-8 but guarded only changes to character_set_client. It did not reject non-UTF-8 character_set_results changes and relied on the server's global session_track_system_variables configuration to report character-set changes. A malicious or compromised server, or a machine-in-the-middle attacker, could suppress tracking or change the result charset so application strings differed from the returned bytes, potentially defeating application-side validation or escaping that depended on the decoded values. This issue is fixed in versions 3.3.7, 3.4.5, and 3.5.11.