Can we add a line to our /etc/hosts file with a hard-coded DNS entry to fix it in the meantime? What's the IP address?
199.16.156.70 twitter.com
104.244.43.231 abs.twimg.com
104.244.43.231 pbs.twimg.com
192.30.253.113 github.com
151.101.24.133 assets-cdn.github.com
[edit: twitter and github are both accessible again.]