The CIA hacks many routers, incl. MikroTik routers.
And: the CIA tools have been stolen and now blackhat hackers worldwide use them.
Search for details of CVE-2018-14847 and CVE-2019-3943
S.a.
https://wikileaks.org/ciav7p1/
http://forum.mikrotik.com/t/statement-on-vault-7-document-release/106907/1
http://forum.mikrotik.com/t/cia-exploits-against-mikrotik-hardware/106871/1
You should allow access to the device only from LAN, or even only from a single LAN-IP, or just a few LAN-IPs.
And keep only secure services, and disable unsecure ones like telnet.
See
https://wiki.mikrotik.com/wiki/Manual:Securing_Your_Router
https://help.mikrotik.com/docs/display/ROS/Securing+your+router