Originally Posted by ajGoes

I hadn't thought of this before, but that's a great reason to use a password manager. It will automatically log you in only to the URL saved with your credentials.

A weakness to this approach is that legitimate sites often change their URLs, so it's not rare that you have to look up the password and re-enter it. Other than turning your skepticism up to eleven, I can't think of a surefire way to avoid absent-mindedly doing that.