Probing Mechanism Relies on Legitimate Browser APIs

LinkedIn loads a 2.7MB deobfuscated JavaScript bundle on every page, containing a hardcoded list of 6,167 Chrome extension IDs paired with specific internal file paths. The code probes each extension sequentially using browser APIs your browser grants freely—no exploits or hacks involved. If a file exists at the path (indicating installation), results are collected, encrypted, and transmitted to LinkedIn servers entirely in the background.

This technique determines exact extension presence without permissions, evading typical detection since it mimics standard resource checks.

Why It's Worse Than Fingerprinting

Unlike canvas or font-based fingerprinting, which infers device traits probabilistically, this directly inventories installed extensions—a unique, persistent identifier. Results enable precise user profiling (e.g., ad blockers, VPNs, productivity tools) for targeting, without privacy policy mention or user consent.

The operation's invisibility and scale make it one of the most invasive documented surveillance systems, legally murky as it leverages allowed APIs rather than vulnerabilities.

BrowserGate: Scale and Stealth

Dubbed 'BrowserGate,' this runs on production pages silently. No user notification occurs, and it's absent from LinkedIn's privacy disclosures. Developers auditing similar bundles can deobfuscate to uncover such lists, revealing targeted extensions for competitive intelligence or personalization.