Telegraf 1.15.3 is a new maintenance release that includes improvements to various plugins, such as Agent, Event Hub Consumer Input, HTTP Listener Input Plugin, Modbus Input, Ping Input, SQL Server Input, and vSphere Input, addressing issues like agent error messages, string conversion errors, and missing cluster names. Additionally, this release enhances the Starlark documentation and adds features for Application Insights Output and Open TSDB Output plugins. The update aims to improve security, extensibility, and overall performance of Telegraf.