# Changelog for Elasticsearch Service Sink Connector for Confluent Platform ## Version 16.0.0 * [PR-940](https://github.com/confluentinc/kafka-connect-elasticsearch/pull/940) - CC-35256: Replaced the deprecated Elasticsearch High Level REST Client `org.elasticsearch.client:elasticsearch-rest-high-level-client` with the Elasticsearch Java API Client `co.elastic.clients:elasticsearch-java` `8.19.19`. The connector now supports Elasticsearch 8.x and 9.x, and no longer supports Elasticsearch 7.x or earlier. For more details, see [Upgrade from version 15.x](overview.md#elasticsearch-sink-upgrade-from-15). * [PR-940](https://github.com/confluentinc/kafka-connect-elasticsearch/pull/940) - CC-35256: Removed the `org.elasticsearch.client:elasticsearch-rest-high-level-client` and `org.elasticsearch:elasticsearch` dependencies to fix CVE-2024-52979, CVE-2024-52980, CVE-2025-37727, and CVE-2025-37731 * [PR-940](https://github.com/confluentinc/kafka-connect-elasticsearch/pull/940) - CC-35256: Changed `max.in.flight.requests` to allow the configured number of concurrent bulk requests instead of one fewer, which can change write ordering for upserts. For more details, see [Upgrade from version 15.x](overview.md#elasticsearch-sink-upgrade-from-15). * [PR-940](https://github.com/confluentinc/kafka-connect-elasticsearch/pull/940) - CC-35256: Changed the connector to require the `X-Elastic-Product: Elasticsearch` response header. For more details, see [Limitations](overview.md#elasticsearch-sink-limitations). * [PR-940](https://github.com/confluentinc/kafka-connect-elasticsearch/pull/940) - CC-35256: Changed `linger.ms=0` and `bulk.size.bytes=0` to be treated as 1 ms and 1 byte respectively, with a one-time warning logged at startup. Observable behavior is unchanged. * [PR-944](https://github.com/confluentinc/kafka-connect-elasticsearch/pull/944) - CC-43920: Fixed an issue where, with `flush.synchronously=false`, consumer offsets stopped advancing when records were dropped before being written, which caused growing consumer lag and reprocessing on restart. * [PR-948](https://github.com/confluentinc/kafka-connect-elasticsearch/pull/948) - Fixed an issue where, with `behavior.on.null.values=delete` and `flush.synchronously=false`, a tombstone record with a null key stopped consumer offsets from advancing and could eventually stall the task. * [PR-945](https://github.com/confluentinc/kafka-connect-elasticsearch/pull/945) - CC-43237: Updated `at.yawk.lz4:lz4-java` to `1.11.3` to fix CVE-2026-59949 * [PR-945](https://github.com/confluentinc/kafka-connect-elasticsearch/pull/945) - CC-43803: Updated `org.apache.logging.log4j:log4j-api` to `2.26.1` to fix CVE-2026-49844