The Festo CECX-X-C1 Modular Master Controller with CoDeSys and CECX-X-M1 Modular Controller with CoDeSys and SoftMotion provide an undocumented access method involving the FTP protocol, which could allow a remote attacker to execute arbitrary code or cause a denial of service (application crash) via unspecified vectors.
https://www.cisa.gov/news-events/ics-advisories/icsa-14-084-01