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)
22.214.171.124 – Quad 9, blocks known malware sites
126.96.36.199 – CloudFlare – Private and unfiltered
188.8.131.52 – Google – Fast DNS
184.108.40.206 – CleanBrowsing – Blocks Adult Sites
220.127.116.11 – Comodo – blocks malware sites
18.104.22.168 – OpenDNS, blocks malware sites, now owned by Cisco
22.214.171.124 – Yandex, blocks malware sites — Russian