Autofill features in browsers and password managers are incredibly convenient—but they can also introduce risks if not configured properly. Attackers can exploit autofill by tricking your browser into filling in credentials on malicious sites.
What Is Autofill?
Autofill is a browser feature that automatically fills in form fields with previously saved information like usernames, passwords, addresses, and credit card details, saving you from typing the same information repeatedly.
For instance, hidden login forms or fake fields embedded in webpages can capture your information without your knowledge. Autofill tools may also populate sensitive data like addresses or credit card numbers on sites you didn't intend.
The Hidden Dangers of Autofill
1. Form Field Confusion
Browsers often can't tell the difference between legitimate form fields and malicious ones. When you visit a website with autofill enabled, your browser might fill hidden fields designed to steal your information.
2. Invisible Form Fields
Attackers can create invisible form fields that your browser will still populate. You might only see one field on screen, but behind the scenes, your browser could be filling in multiple fields with sensitive information.
Attack Example: The Hidden Field Attack
Imagine visiting what looks like a simple newsletter subscription form asking only for your email. Behind the scenes, the page could contain hidden fields for name, address, phone number, and even credit card details. When you click in the email field, your browser might autofill all these hidden fields, giving the attacker information you never intended to share.
3. Cross-Site Autofill
Some browsers might autofill credentials from one site onto a similar-looking but completely different site. This makes phishing attacks much more dangerous—if you're tricked into visiting a fake version of your bank's website, your browser might helpfully fill in your banking credentials.
4. Over-Eager Form Filling
Even when you just click on a single field, your browser might fill in multiple related fields. For example, clicking on an address field might trigger autofill to populate your full name, address, phone number, and email.
Continue Reading
Learn how to configure autofill safely, choose between password managers and browser autofill, and find the right balance between convenience and security.
Part 2: Using Autofill Safely →