WAC on the Sangfor Sundray WLAN Controller version 3.7.4.2 and earlier has a backdoor account allowing a remote attacker to login to the system via SSH (on TCP port 22345) and escalate to root (because the password for root is the WebUI admin password concatenated with a static string).
Source: NIST
CVE-2019-9160 (sundray_wan_controller_firmware)