How to disable auto-signin feature?

I, too, was affected after the most recent update when logging in to my health insurance site, https://www.nebraskablue.com/member-login (click the Login button to get to the actual form). On the login form, they have a "Login as Guest Member" button beneath the disabled "Login" button. I suspect the "as guest" button is the action that gets selected by default when the form is submitted as a form of bot protection. Looking at the HTML code for the page, I can't explain why that button would be selected instead of the button labeled "Login". While the form inputs are empty, the "Login" button is disabled, but is enabled once the values have been filled out, so there may be a timing issue -- like the submission is happening too fast.

I had a similar issue on a form I was working on with an auto-filled date-of-birth. When the form was submitted via AJAX, the DOB was empty because the validate/store method was called on the change and input actions, which were never triggered by the auto-fill. I was able to replicate the behavior by changing the field value in the dev console. Does the extension click the first enabled button with a name like "Login" or "Sign In"? If so, that would explain my experience.

The behavior is the same in Chrome and Safari when using the auto-submit feature, and this site was the only site I experienced an issue with. For now, I'm content with turning off the auto-submit. Please let me know if I can provide more information.