Beckhoff Embedded Windows PLCs through 3.1.4024.0, and Beckhoff Twincat on Windows Engineering stations, allow an attacker to achieve Remote Code Execution (as SYSTEM) via the Beckhoff ADS protocol.
https://www.ic4.be/2019/12/18/beckhoff-cve-2019-16871/#more-648
https://download.beckhoff.com/download/document/product-security/Advisories/advisory-2017-001.pdf