AliExpress accused of fingerprinting shoppers with silent audio trick that also muted a dev's headphones
Sawtooth waves you can't hear still mess with your Bluetooth. Firefox and Brave say they've got you covered
Developer Matt Callaghan discovered that the AliExpress website uses audio fingerprinting to track web users, even when their Bluetooth headphones are muted. Callaghan noticed his headphones stopped playing music when he visited AliExpress on Firefox or Chrome. Further investigation revealed hidden audio scripts within AliExpress' browser security and anti-abuse tooling that generated a sawtooth waveform, measured the result, and read the frequency data without playing any audio.
This allowed Alibaba to maintain the user's Bluetooth audio path, preventing their headphones from switching to the phone. While Firefox claims its anti-fingerprinting technology can thwart AliExpress' tracking, the developer found that only 99.24% of users fall into three "buckets" that the protection eliminates. The remaining 0.76% of users, including Callaghan, are not as effectively protected.
Brave and Safari have also implemented measures to protect users from this audio fingerprinting technique.
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