far more likely that your browser is set up to automatically enter your details in forms.
You using chrome ?
That would know all your details and it's the kind of 'useful' thing it tends to do.

There are sooooo many reasons not to use chrome or edge. That's just one of them.
Dunno about safari.

But yeah, it's your browser filling in the form NOT the form stealing your data.

So most likely your end, not the survey end.