Telegraf 1.21.4 has been released, addressing security vulnerabilities and introducing updates to various plugins, including Docker Input Plugin, JSON v2 Parser, and Go library, as well as adding new external plugins such as apt and knot for collecting stats from Knot DNS. The release includes fixes for issues with timestamp handling, memory usage calculation, and deprecated warnings for PreVista support. Additionally, the update includes dependencies updates to various libraries and frameworks, including Go, OpenTelemetry, and Kubernetes.