Being prompted for password on guest user when asked if i want to trust a certificate

Here are some steps that may help. It is important to back up your Mac before troubleshooting.

1. Ensure the date and time are set automatically.
2. Connect your Mac to the internet using a different known good network.
3. Restart your Mac.
4. Create and set up a temporary admin user without signing in with an Apple ID.

If the issue persists from the temporary admin user, continue troubleshooting with the following steps.

• Update your Mac.
• Erase your Mac and then install a clean copy of macOS.

If the issue does not persist from the temporary admin user, contact Apple Support for further assistance.

I take it that you are NOT logged as guest when you see this.

First make sure that you do trust that website. It may have an expired certificate or something, and be ok.

If that is the case, simply type your own username and password.

I see this sometimes, except that instead of guest user it prompts with the name of a different account (in my case, a second admin account); when this happens I can either type the password for that account or enter my own username and password. They both work.