Anthropic has removed a secret tracking feature from its Claude Code tool after a researcher exposed the code last week. The company had used the tracker since March to monitor users in China. Alibaba banned employee use of the tool in response.
A web developer known as Thereallo discovered the hidden code while researching privacy issues. The tracker used prompt steganography to send data on timezones, proxies, and potential links to Chinese AI labs without user detection.
Anthropic engineer Thariq Shihipar confirmed on X that the feature was an experiment to prevent account abuse and distillation attacks. He said the company had planned to remove it after developing stronger protections.
Last Friday Alibaba issued a memo banning Claude Code for work, citing security vulnerabilities from the tracker. The move follows accusations that Chinese firms have used distillation to copy US models like Claude.
Privacy advocates criticized the secret tracking. Thereallo stated that hiding the signal makes other privacy claims harder to believe.
