Browser extensions can be fingerprinted and tracked through web accessible resources and visible side effects.
- Browser extensions can be easily fingerprinted through static extraction or behavioral fingerprinting.
- Developers can stop static extraction by referencing images and CSS from websites or CDNs.
- Behavioral fingerprinting is more difficult to get rid of because it requires extra UI buttons and ad blockers.
- The middle way combines the best of both worlds by using CSS-based extension fingerprinting.
- Web accessible resources can be used to unmask browser extensions.
- Visible side effects of extensions can be used to fingerprint and track them.
- A system can automatically compare a page with and without an extension to detect changes that could be used to fingerprint.