Anthropic VS code extension on Cursor backdoored for nearly 12 hours

Live updates

1. 1h ago

   Anthropic Claude Extension Backdoored on Cursor Marketplace

   A malicious version of Anthropic's official Claude Code extension was distributed through the Cursor Marketplace as a legitimate update, exposing developer devices to a persistent SSH backdoor and credential theft. Cursor stated that up to 5,000 users were affected across versions 2.1.312 and 2.1.313 for Windows and macOS. The compromised package was available for nearly 12 hours before being removed. Security researchers discovered the trojanized update, prompting Cursor to temporarily shut down its marketplace to pull the malicious package.

   Why it matters

   Software development environments are increasingly targeted by supply chain attacks that exploit trusted publisher channels and auto-update mechanisms. Because extensions often run with elevated permissions, a single compromised update can install persistent remote access tools on developer machines. This incident highlights the vulnerability of integrated development environment marketplaces where third-party packages can be manipulated.

   What is confirmed

   • A trojanized version of Anthropic's official Claude Code extension was distributed through the Cursor Marketplace.
   • The malicious update was published as versions 2.1.312 and 2.1.313 for Windows and macOS.
   • Cursor reported that up to 5,000 users were affected by the tampered extension.
   • The compromised package attempted to install a persistent SSH backdoor across macOS, Linux, and Windows.
   • The unauthorized update remained available on the Cursor marketplace for nearly 12 hours.

   Still unconfirmed

   • The malicious code specifically aimed to steal cloud credentials.
   • Attackers gained access to Anthropic's verified Cursor account.
   • Anthropic has not issued a formal customer warning regarding the incident.

   What to watch next

   • Official clarification on how attackers gained access to the publisher account
   • Additional security audits from Cursor regarding marketplace extension verification
   Sources used for this update (17)

   1. arstechnica.com — Ars Technica - Serving the Technologist since 1998. News, reviews, and ...
   2. feedly.com — CVE-2026-86988 - Exploits & Severity
   3. WIRED — A Supply Chain Attack Put Malicious Anthropic Claude Extensions on Thousands of Devices
   4. Reuters — Cursor says up to 5,000 users affected by tampered Claude Code extension
   5. Microsoft — Inside a malicious Claude Code-branded extension and its persistent SSH backdoor
   6. DoublePulsar — Anthropic hacked to deliver remote access trojan to Claude developer laptops worldwide
   7. Ars Technica — Anthropic VS code extension on Cursor backdoored for nearly 12 hours
   8. opensourcemalware.com — Trojanized Claude Code Extension Plants an SSH Backdoor | OpenSource Malware Blog
   9. phorion.io — Official Claude Code Extension Compromise: Security Advisory | Phorion
   10. arstechnica.com — Anthropic VS code extension on Cursor backdoored for nearly ...
   11. cursor.com — Security notice — malicious version of Anthropic.claude-code ...
   12. cursor.com — 보안 공지 — Cursor VS Code 확장 프로그램 마켓플레이스에서 Anthropic.claude-code 악성 버전(2.1.312 및 2.1.....
   confidence 95%