Those three links don't really relate to third parties getting unauthorised access through phishing by leveraging Slack. Slack has plenty of security issues, but you're not proving phishing by any of those sources. It can potentially make you more vulnerable to phishing, but that's not the same thing.

The links in question relate to:

* Searching on GitHub for Slack API tokens

* The Slack database hack

* How the rise of ChatOps can open you up to many more issues if someone gains access to employee's Slack accounts and the risk of third-party applications which might open up things you do to more entities than you realise