Draytek Routers have an acknowledged 0 Day. It has been seen in the wild!
One of the indicators that your router has been compromised is changing of your DNS Settings. A change of DNS will allow Cyber Criminals to impersonate other websites allowing the bad guys to siphon your personal information.
It is a good idea to periodically check all your devices DNS Settings anyway.
A list of recommend DNS Server are (in no particular order)
126.96.36.199 – Quad 9, blocks known malware sites
188.8.131.52 – CloudFlare – Private and unfiltered
184.108.40.206 – Google – Fast DNS
220.127.116.11 – CleanBrowsing – Blocks Adult Sites
18.104.22.168 – Comodo – blocks malware sites
22.214.171.124 – OpenDNS, blocks malware sites, now owned by Cisco
126.96.36.199 – Yandex, blocks malware sites — Russian