Prevent Keychain from copying an internet password to my login keychain I find that my passwords are being copied from my "bank" keychain into the login keychain every time I allow Safari to autofill the fields. How can I prevent that?

I have created a separate keychain called "bank" to store my sensitive financial account passwords. I use a different keychain password and set it to lock automatically after 5 minutes.
This was a security bug and a fix was released today by Apple.

About the security content of Safari 10.1:

Safari Login AutoFill


  Available for:  OS X Yosemite v10.10.5, OS X El Capitan v10.11.6,
  and macOS Sierra 10.12.4
  
  Impact: A local user may be able to access locked keychain items
  
  Description: A keychain handling issue was addressed through improved keychain item management.
  
  CVE-2017-2385: Simon Woodside of MedStack