OpenVPN version 2.4.0 through 2.6.10 on Windows allows an external, lesser privileged process to create a named pipe which the OpenVPN GUI component would connect to allowing it to escalate its privileges
https://www.cisa.gov/news-events/ics-advisories/icsa-25-072-10
https://www.mail-archive.com/[email protected]/msg07634.html