Since the recent macOS 10.14.4 update which includes Safari 12.1 (14607.1.40.1.4), last started to automatically submit web forms with login & password fields once a value for password or login is selected from auto-fill options. This seems to be related to the new 10.14.4 feature where Touch ID got an option to confirm auto-fill in Safari. However I have it switched off but Safari still does this crap. I'm curious if anyone else have the same problem and how to solve it.
I have this issue too, and I've just spent a long time with an Apple Support chat agent.
This is a "feature" introduced in Safari 12.1.
Streamlines website login when filling credentials with Password AutoFill.
There is currently no way to turn this off. This is the solution the agent proposed. Submit a feedback to Apple:
...submit your feedback on the feature and your experience so far.
Maybe if we kick up enough of a fuss? It is a pain, and it also screws with captchas quite impressively...
You can use StopTheMadness Safari extension to switch off auto submit behavior.
I got the same issue with Safari 12.1, but I think it's not so bad 1. For sites which require captcha, the form is working like before, does not auto submit 2. For other sites, I got issue when can not click 'Remember me', but at the end I just click to that option first, and fill username & password.
So, I am totally fine with this feature.