Cascading Spy Sheets: Exploiting the Complexity of Modern CSS for Email and Browser Fingerprinting
Leon Trampert
Network and Distributed System Security (NDSS) Symposium 2025 · Day 2 · Email Security
In "Cascading Spy Sheets," Leon Trampert from Sisba unveils a novel and potent method for user fingerprinting that leverages the intricate capabilities of modern CSS, effectively circumventing traditional JavaScript-based detection. This talk highlights how the seemingly innocuous Cascading Style Sheets, a fundamental component of web rendering, can be weaponized to extract a wealth of information about a user's browser, operating system, hardware, and even installed applications, even in environments where JavaScript execution is disabled or unavailable.
AI review
Genuinely novel attack surface — CSS as a side-channel for fingerprinting in JS-free environments, extended to email clients, is not something the community has fully mapped. The container-query width oracle and calc() floating-point divergence across CPU architectures are clever, original primitives. Solid enough to matter, though the email client study methodology (21 clients, ~100 emails each, manual opening) leaves the empirical bar lower than it should be for a claim this broad.