Plague: A Newly Discovered Pam-Based Backdoor for Linux(nextron-systems.com)
nextron-systems.com
Plague: A Newly Discovered Pam-Based Backdoor for Linux
https://www.nextron-systems.com/2025/08/01/plague-a-newly-discovered-pam-based-backdoor-for-linux/
The xz backdoor was such because it was stealthily slipped in with the vendor's original software, without their knowledge, and no further attack or action by the user was required to install it.
The Juniper backdoor a few years ago qualified per the same criteria.