Pi-hole is a DNS sinkhole that protects devices from unwanted content without installing any client-side software. From 6.0 to 6.4.2, a user with code execution as the unprivileged pihole user can escalate to root by replacing /etc/pihole/logrotate. The replacement is laundered to root:root ownership by pihole-FTL-prestart.sh and then parsed as root by the daily pihole flush cron, executing firstaction shell as uid 0. This issue is fixed in version 6.4.3.
https://github.com/pi-hole/pi-hole/security/advisories/GHSA-h8w9-qx2v-wrww
https://github.com/pi-hole/pi-hole/releases/tag/v6.4.3
https://github.com/pi-hole/pi-hole/commit/18002bf7c6bf382fe5861d01321f427019e1be89