From mid 2014 to January 2018, Discourse used Slack as an internal chat tool.
In February 2015, Slack had a security incident
[https://slackhq.com/march-2015-security-incident-and-the-launch-of-two-factor-authentication]
, and notified any accounts of "suspicious activity":
> As part of our investigation we detected suspicious activity affecting a very
small number
