Password-protected posts trigger login interface?

Good day.

I’m working on a theme for my employer and I’ve run into an odd situation. If I password protect a post, navigate to it, input the password and press enter, I’m sent to the account authorization page on my account management service. It’s exactly as though I had just logged in, and then get navigated to the wp-admin page.

This only happens when I have the plugin set to Auto Login-SSO; it’s perfectly well behaved otherwise.

Any ideas?