(Lab Note: Click the "Full Name" field and select your saved profile from the browser's Autofill dropdown)
Data Exfiltrated!
You thought you only submitted your Name and Email. Here is what the browser secretly auto-filled in the hidden fields:
> Name:
> Email:
> --- STOLEN DATA ---
> Phone:
> Address:
> Organization:
Developer Notes:
Autofill is a massive UX improvement, but it is inherently dangerous. If a user clicks "Autofill" on a seemingly innocent field (like Name), the browser will eagerly fill every corresponding autocomplete="..." field it finds on the page, even if the developer has visually hidden them off-screen using CSS.
Lesson: Users must be extremely cautious about using browser autofill on untrusted sites.