This ersatz Login window appeared this morning one time. It did nothing and I fear credential harvesting:
1PW wouldn't fill it, it didn't work, I closed Safari window and opened a new one. It did not appear again.
I took steps to change my password and add additional security.
I'm thinking this is something running locally on my MacBook Pro. Safari 12.0.3, macOS 10.13.6 High Sierra.
Do you recognize it?
1Password Version: 7.1.2
Extension Version: 4.7.3
OS Version: OSX 10.13.6
Sync Type: Dropbox
Referrer: forum-search:"Your login information will be sent securely."