Since Chromium 148, Math.tanh is now fingerprintable to link underlying OS
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Chrome 148 changed Math.tanh to call the OS math library, leaking the underlying OS.
Since Chrome 148, V8 replaced its bundled fdlibm port for Math.tanh with std::tanh, which calls the host libm. This makes tanh(0.8) return different bits on Linux, macOS, and Windows, enabling OS fingerprinting via a single JavaScript call. CSS trig functions and Web Audio also leak OS math libraries. Scrapfly reverse-engineered Apple's libsystem_m and maps Windows UCRT to reproduce genuine browser math bit-for-bit in its headless browser. The article details the code paths, pitfalls (FMA, scalar vs. vector math), and validation methods.
What commenters are saying
Commenters note the article reads like LLM-generated content, with multiple users identifying it as likely written by Claude. Some debate the merits of fixed-point math over floats for determinism and precision in computational work. One commenter points out that most users are already fingerprintable by IP and user agent, while another suggests correctly rounded transcendental functions would eliminate this leak. A few discuss the difficulty of correctly rounding pow() and the table-maker's dilemma.