Anthropic reports malicious actor exploited Cursor marketplace to release tampered Claude Code extension.
anthropic claude cursor
| Source: Techmeme | Original article
Anthropic reports that a malicious actor exploited Cursor's marketplace to release a tampered version of the Claude Code extension, which Anthropic did not create or publish.
Anthropic confirmed that a malicious actor exploited the Cursor VS Code extension marketplace to publish a tampered version of the “Claude Code” plug‑in. The rogue package, which appeared for roughly eleven hours on Thursday, was not created or released by Anthropic and was never hosted on the company’s official channels. According to technical staff member Felix Rieseberg, the attacker used their access to Cursor’s marketplace to upload the compromised copy, which then attempted to harvest system details – hostname, username, operating system and public IP – and to establish remote‑access footholds on affected machines. Anthropic says no Anthropic systems or employee laptops were breached; the incident is confined to Cursor users, estimated at up to 5,000.
The episode underscores the growing risk of supply‑chain attacks on AI tooling. As developers increasingly rely on third‑party extensions to integrate large‑language models like Claude into their workflows, a single compromised marketplace can expose thousands of users to data exfiltration and malware. The incident follows a recent Anthropic security breach that delivered a remote‑access trojan to developer laptops, highlighting a pattern of adversaries targeting the ecosystem surrounding the company’s models.
Anthropic is working with Cursor to remediate the malicious extension and to tighten marketplace controls. Observers will watch for any further disclosures from Cursor about how the attacker gained publishing rights, as well as any broader response from the VS Code extension ecosystem. Additional scrutiny of code‑signing practices and provenance verification for AI‑related plugins is likely to intensify, and developers should verify the source of extensions before installation. The episode serves as a reminder that securing the supply chain is now as critical as protecting the models themselves.
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