An issue was discovered in BeyondTrust Privilege Management for Windows through 5.6. An attacker can spawn a process with multiple users as part of the security token (prior to Avecto elevation). When Avecto elevates the process, it removes the user who is launching the process, but not the second user. Therefore this second user still retains access and can give permission to the process back to the first user.
https://www.beyondtrust.com/trust-center/security-advisories/bt22-11
https://www.beyondtrust.com/support/changelog/privilege-management-for-windows-5-6-sr1