When adding a secret broke CI in GitHub

Fun story, we had some URLs hard-coded in our CI scripts for various environments. Then later someone added the same string as one of these URLs as a repo secret in GitHub. Suddenly every CI job using the hard-coded version of that URL started failing. The reason being, GitHub started replacing the URL with "***", because it thinks it's being slick censoring something that appears in secrets.

So that's how you can break your CI by just adding a secret.