A remote attacker might be able to cause infinite recursion in PowerDNS Recursor 4.8.0 via a DNS query that retrieves DS records for a misconfigured domain, because QName minimization is used in QM fallback mode. This is fixed in 4.8.1.
https://docs.powerdns.com/recursor/security-advisories/
https://docs.powerdns.com/recursor/changelog/4.8.html#change-4.8.1