Privacy threats of browser form autofill

• Attack Demos
  • Inter email address from multiple profiles
  • Infer credit card number from 100k candidate values
  • Infer phone number from 100k candidate values
  • Generate and distribute candidate values
• Extension
• Crawling
  • Patch
  • Crawler
• Data
• Research Paper

Attack demos

A novel, complicated side-channel attack that exploits browser’s autofill preview functionality to infer information in user's profile.

The demos are for educational and demonstration purposes only!

Installation

The attack_demos folder needs to be uploaded to the public folder on webserver.

Inter email address from multiple profiles

multiple_emails.html: obtain the email addresses from multiple profiles in the autofill.

The page infers the email address from 40,463 candidate values.

Affected browsers: prior to 89.0.4389.72.

Affected versions: all.

1. Set up the address profile on Chrome.

Settings -> Autofill -> Addresses and more.

Set the email address between [email0, email40462]. You may have multiple profiles.

2. Visit the page at http://yourdomain.com/attack_demos/multiple_emails.html

3. Click the input field and mouse over different profiles. The page displays the results immediately.

Infer credit card number from 100k candidate values

preview_cc.html: infer user's credit card number from 102k candidate values. Payment autofill requires https connection.

Affected browsers: all Chromium-based browsers.

Affected versions: prior to 84.0.4147.89.

1. Set up the payment profile on Chrome.

Settings -> Autofill -> Payment methods

Set the credit card number between [4123456789000000 - 4123456789100333].

2. Visit the page at https://yourdomain.com/attack_domos/preview_cc.html.

3. Click the input field and mouse over the profile. There are a few seconds delay before the page shows the result, depending on the device.

Infer phone number from 100k candidate values

preview_phone.html: infer user's phone number from 102k candidate values.

Affected browsers: all Chromium-based browsers.

Affected versions: prior to 84.0.4147.89.

1. Set up the address profile on Chrome.

Settings -> Autofill -> Addresses and more.

Set the phone number between [1234000000 - 1234100866].

2. Visit the page at http://yourdomain.com/attack_demos/preview_phone.html

3. Click the input field and mouse over the profile. There are a few seconds delay before the page shows the result, depending on the device.

Generate and distribute candidate values

1. generate and distribute 40k email addresses to 199 <select> elements.

python3 attack_demos/menu_generator_py/generate_html.py

2. generate and distribute 100k phone numbers to 198 <select> elements.

python3 attack_demos/menu_generator_py/generate_html_phone.py

3. generate and distribute 100k credit card numbers to 198 <select> elements.

python3 attack_demos/menu_generator_py/generate_html_cc.py

Extension

A chrome extension that detects autofillable, hidden elements in a visitied page. It shows a warning message on lax mode, and remove these hidden elements on strict mode.

Crawling

Patch

We provide the source code modification as a patch to Chromium.

Crawler

The crawler is running on top of Selenium and an intrumented Chromium (Version 81.0.4009.0) / Firefox (Nightly Version 74).

Data

In a crawl conducted during November 2019, these web pages were found to have hidden HTML elements autofilled by Chrome/Firefox.

Research Paper

You can read more about the details of our work in the following research paper:

Fill in the Blanks: Empirical Analysis of the Privacy Threats of Browser Form Autofill

If you use our code, data, or otherwise conduct research related to our work, please cite our paper PDF:

@inproceedings{lin2020fill,
  title={Fill in the Blanks: Empirical Analysis of the Privacy Threats of Browser Form Autofill},
  author={Lin, Xu and Ilia, Panagiotis and Polakis, Jason},
  booktitle={Proceedings of the 2020 ACM SIGSAC Conference on Computer and Communications Security},
  pages={507--519},
  year={2020}
}