Official Anthropic Claude Extension on Cursor Backdoored; Up to 5,000 Users Affected

5.4 · 1d ago · WORLD · AI

The Facts

  • Version 2.1.313 of Anthropic's official Claude VS Code extension, distributed through Anthropic's official account on Cursor's marketplace, was backdoored. Ars Technica only
  • Cursor said the malicious version affected at most 5,000 users. Ars Technica only
  • Anthropic pushed version 2.1.314 several hours after the malicious version became available, according to independent researcher Kevin Beaumont; the headline says the backdoor lasted nearly 12 hours. Ars Technica only
  • Phorian CTO and co-founder Luke Roberts described it as a supply-chain compromise in which the attacker gained access to the official distribution channel; 2.1.313 superseded 2.1.312. Ars Technica only
  • Extensions auto-update in Cursor by default, though users can change this in settings. Ars Technica only
Dive deeper · 1 more factShow less
  • Neither Cursor nor Anthropic has explained how attackers gained control of the account, and Anthropic had not yet warned customers as of Ars Technica's report. Ars Technica only

Context

A malicious version of Anthropic's official Claude extension for VS Code was published to Cursor's extension marketplace, according to Ars Technica. Cursor said at most 5,000 users were affected.

Security researchers say the attacker gained access to Anthropic's official distribution channel. The method of compromise has not been disclosed by Cursor or Anthropic.

How the Agent Panel Scored This

Independent AI personas each scored importance 1–10; the story's score is a trimmed mean (highest and lowest votes dropped). Vote spread: 2.

6 News Editor A concrete supply-chain compromise of a widely used official AI developer extension affecting up to 5,000 users is newsworthy with real security impact, but the scale is limited and the story is a niche developer-tool security incident rather than broad public-impact news.
6 Critical Reader A concrete, verified supply-chain compromise of a major AI vendor's official extension affecting up to 5,000 users with auto-update, but the scale is modest and key details like the attack method remain undisclosed.
6 Policy Expert A concrete security incident in which a malicious version of a widely used official extension was distributed to up to 5,000 users, with auto-update enabled, is newsworthy with moderate-to-significant impact, though limited to a single marketplace and a bounded user count.
5 Business Analyst A supply-chain backdoor in a major AI vendor's official extension affecting up to 5,000 users is a notable security incident with real impact, but its scale is limited and it is not market-moving.
5 Science & Tech Analyst A supply-chain backdoor in a widely used official AI developer extension affecting up to 5,000 users is a notable security incident with moderate, concentrated impact, though its scope is limited and the story is from a single source.
5 Informed Citizen A concrete supply-chain compromise of a widely used official AI coding extension affecting up to 5,000 users with auto-update risk is newsworthy and security-relevant, but its reach is limited to a single marketplace and a few thousand users, and the backdoor window has closed.
4 Global Affairs Analyst A supply-chain backdoor in a widely used official AI developer extension affecting up to 5,000 users is a notable cybersecurity incident, but its scope is limited and it is not major geopolitical news.

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