RouterOS versions 6.45.6 Stable, 6.44.5 Long-term, and below allow remote unauthenticated attackers to trigger DNS queries via port 8291. The queries are sent from the router to a server of the attacker's choice. The DNS responses are cached by the router, potentially resulting in cache poisoning
https://www.tenable.com/security/research/tra-2019-46
http://packetstormsecurity.com/files/155036/MikroTik-RouterOS-6.45.6-DNS-Cache-Poisoning.html