DrayTek Vigor2960 1.3.1_Beta, Vigor3900 1.4.4_Beta, and Vigor300B 1.3.3_Beta, 1.4.2.1_Beta, and 1.4.4_Beta devices allow remote code execution as root (without authentication) via shell metacharacters to the cgi-bin/mainfunction.cgi URI. This issue has been fixed in Vigor3900/2960/300B v1.5.1.
https://thehackernews.com/2023/12/behind-scenes-of-matveevs-ransomware.html
https://sku11army.blogspot.com/2020/01/draytek-unauthenticated-rce-in-draytek.html