Cursor says up to 5,000 users affected by tampered Claude Code extension

Live updates

1. 50m ago

   Tampered Claude Code Extension Affects Up to 5,000 Cursor Users

   Up to 5,000 users may have installed a maliciously modified version of Anthropic's Claude Code extension on the Cursor VS Code extension marketplace. The compromised software attempted to install a persistent SSH backdoor and harvested sensitive system data such as usernames, hostnames, operating systems, and public IP addresses. Cursor removed the malicious upload from its marketplace and verified that no other extensions were affected. Anthropic confirmed it was not involved in building, publishing, or hosting the tampered extension.

   Why it matters

   Supply chain attacks targeting developer tools present severe security risks because developers often grant elevated privileges to coding assistants and extensions. A backdoor installed on a developer machine can compromise entire code repositories and downstream enterprise infrastructure. Companies continue to audit software marketplaces to prevent malicious actors from impersonating trusted AI coding tools.

   What is confirmed

   • Cursor stated that a maliciously modified version of Anthropic's Claude Code extension was available on its Cursor VS Code extension marketplace, affecting up to 5,000 users.
   • The modified extension appeared on the marketplace on Thursday between 5:27 AM ET and 4:35 PM ET.
   • The extension contained malicious code designed to collect hostname, username, operating system, home directory path, and public IP address.
   • Cursor removed the malicious extension from its marketplace and verified that no other extensions were tampered with.
   • Anthropic stated it was not involved with building, publishing, or hosting the extension.

   Still unconfirmed

   • The attack likely failed on most machines due to admin rights.

   What to watch next

   • Forensic analysis detailing how the malicious extension bypassed marketplace verification
   • Confirmation from security researchers on how many machines were successfully backdoored
   • Official guidance from Cursor and Anthropic for affected users to remediate compromised systems
   Sources used for this update (23)

   1. thehackernews.com — The Hacker News | #1 Trusted Source for Cybersecurity News
   2. www.helpnetsecurity.com — Cybersecurity News and Expert Analysis - Help Net Security
   3. www.marketscreener.com — Global Stocks Fall on Higher Oil Prices, AI Pullback | MarketScreener
   4. www.channelnewsasia.com — NATO general sets out tough military response to any 'foolish' Russian attack - CNA
   5. www.thestar.com.my — AI worries expose dollar's hot-money problem
   6. thenextweb.com — Apple launches its first touchscreen MacBook Pro, from $2,899
   7. blakecrosley.com — Claude Code CLI: The Complete Guide — Hooks, MCP, Skills
   8. superpowerdaily.com — AI data-center borrowers face higher costs as lenders struggle to absorb more debt
   9. gptonline.ai — ChatGPT Adds ICloud Mail And Calendar Plugins On All Plans
   10. 1023jack.com — Anthropic Could Go Public With A “Junk” Credit Rating. What That Means, And What Is Actually Confirmed
   11. WIRED — A Supply Chain Attack Put Malicious Anthropic Claude Extensions on Thousands of Devices
   12. Reuters — Cursor says up to 5,000 users affected by tampered Claude Code extension
   confidence 100%