Elon Musk and Substack are beefing. Here's a rundown of the back and forth between the Twitter CEO and the blogging site.

• Twitter users began noticing Substack links were being suppressed beginning Thursday evening. 
• Musk denied the links were "blocked" but said he believed that Substack was "unsafe."
• Substack CEO Chris Best pushed back on Musk's assertions Saturday evening.

Over the past few days, a war between subscription-based blogging website Substack and microblogging platform Twitter has been brewing — with the CEOs of both platforms publicly responding to the controversy.