Challenge text suggested to lookup, took this to be a pointer for dns lookup, lucky guess

fire off dig to get all records we get a base64 string in the txt record

`dig any bitsctf.cf`

* ; <<>> DiG 9.11.5-P1-1-Debian <<>> any bitsctf.cf
* ;; global options: +cmd
* ;; Got answer:
* ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 35558
* ;; flags: qr rd ra; QUERY: 1, ANSWER: 7, AUTHORITY: 0, ADDITIONAL: 1
*
* ;; OPT PSEUDOSECTION:
* ; EDNS: version: 0, flags:; udp: 512
* ;; QUESTION SECTION:
* ;bitsctf.cf. IN ANY
*
* ;; ANSWER SECTION:
* bitsctf.cf. 3599 IN SOA ns31.cloudns.net. support.cloudns.net. 2019020101 7200 1800 1209600 3600
* bitsctf.cf. 3599 IN A 35.226.250.134
* bitsctf.cf. 3599 IN NS ns32.cloudns.net.
* bitsctf.cf. 3599 IN NS ns33.cloudns.net.
* bitsctf.cf. 3599 IN NS ns31.cloudns.net.
* bitsctf.cf. 3599 IN NS ns34.cloudns.net.
* bitsctf.cf. 3599 IN TXT "L25vZGUvZG5zLXRyb3VibGU="
*
* ;; Query time: 100 msec
* ;; SERVER: 8.8.8.8#53(8.8.8.8)
* ;; WHEN: Tue Feb 05 12:34:36 CET 2019
* ;; MSG SIZE rcvd: 223

decoding using base64 -d we get
/node/dns-trouble

Hitting the page, came up with nothing until checking the headers, the flag was in the X-Flag: response header

`BITSCTF{7h15_w45_345y_dn5}`