@emptybottle - I don't know why this is happening, but it is:

"Warning: Potential Security Risk Ahead

Firefox detected a potential security threat and did not continue to doc.tidalcycles.org. If you visit this site, attackers could try to steal information like your passwords, emails, or credit card details.

What can you do about it?

The issue is most likely with the website, and there is nothing you can do to resolve it. You can notify the website’s administrator about the problem."

Same here. I didn’t submit the link as doc.tidalcycles.org either, it should have been the root of the domain which does work.

You submitted https://tidalcycles.org, but that page specifies https://doc.tidalcycles.org/ as its canonical URL:

  <link data-react-helmet="true" rel="canonical" href="https://doc.tidalcycles.org/">

Our software replaces the submitted URL with the canonical URL when it finds one.