A flaw discovered in Google's Bluetooth Low Energy Titan Security Keys leaves a hole open for potential attackers. Under certain circumstances and with proper timing, an attacker could potentially hijack the Bluetooth pairing process used by the Titan to log into a user's account. Google has offered to replace affected Titan Security Keys free of charge.
https://www.notebookcheck.net/Security-flaw-found-in-Google-s-Titan-Security-Keys.420756.0.html