An official VS Code extension for Anthropic’s Claude model has been compromised with a backdoor, threatening the machines of up to 5,000 developers. The malicious package, identified as version 2.1.313, was available in the marketplace of Cursor, a maker of AI-assisted developer tools, and was distributed directly through Anthropic’s official account.
Luke Roberts, CTO and co-founder of the security firm Phorian, described the incident as a supply-chain breach in which hackers successfully infiltrated the official distribution pathway. Because extensions on the Cursor platform update automatically by default, the compromised software affected up to 5,000 users who either downloaded it manually or received it through automated background processes. In response to the issue, Anthropic released the corrected version 2.1.314 a few hours later.
Despite the severity of the attack, which reportedly searched for cloud credentials, neither Cursor nor Anthropic has explained how unauthorized actors managed to take control of the official account. Multiple sources noted that Anthropic has not yet issued a formal warning to its customers regarding the security incident. Independent researcher Kevin Beaumont and Phorian executives confirmed that the malicious update was posted directly through the company's verified account.