{
 "license": "CC-BY-4.0",
 "attribution": "Fide AI, Agentic Cyber Explorer",
 "url": "https://agentic-cyber-explorer.pages.dev/events/cursor-claude-code-marketplace-compromise-2026/",
 "asOf": "2026-10-30",
 "id": "cursor-claude-code-marketplace-compromise-2026",
 "date": "2026-10-29",
 "datePrecision": "day",
 "title": "Cursor reports a malicious Claude Code extension build in its marketplace affected at most 5,000 users",
 "lane": "attack",
 "kind": "incident",
 "summary": "Cursor reports that a maliciously modified Claude Code extension, version 2.1.313, was distributed through its extension marketplace on October 29. Cursor says at most 5,000 users were affected; the build collected host information and attempted persistent remote access, with success constrained by host privileges and code errors.",
 "whyItMatters": "It documents a compromise of a coding assistant distribution channel, distinct from a prompt-injection demonstration.",
 "actors": [
  "cursor",
  "anthropic"
 ],
 "topics": [
  "agent-supply-chain",
  "data-exfiltration",
  "incident-reporting"
 ],
 "atlas": [
  "supply-chain",
  "credentials"
 ],
 "artifacts": [],
 "sources": [
  {
   "url": "https://cursor.com/blog/claude-code-extension-security-notice",
   "publisher": "Cursor",
   "title": "Security notice — malicious version of Anthropic.claude-code (2.1.313) identified in the Cursor Extension Marketplace",
   "date": "2026-10-29",
   "type": "primary",
   "accessed": "2026-10-30"
  }
 ],
 "keyFacts": [
  {
   "fact": "Cursor places distribution between about 02:27 and 13:35 Pacific time on October 29 and says the malicious build was not developed by Anthropic. The affected-user ceiling does not establish successful remote access on every host.",
   "locator": "What happened"
  },
  {
   "fact": "Cursor reports removing the build, auditing other extensions, rotating keys, rebuilding the marketplace and taking the attacker server offline with its provider.",
   "locator": "What we did"
  },
  {
   "fact": "Cursor says the remote-access step fails on hosts where the extension lacks the required administrator privileges, while host reporting and persistence still warrant remediation. It reports no evidence affecting other versions or the official distribution.",
   "locator": "What happened; What you should do"
  }
 ],
 "significance": 4,
 "fideQuestions": [
  "FID-077"
 ],
 "methods": [
  "malicious-agent-extensions"
 ],
 "review": "assistant-drafted",
 "addedOn": "2026-10-30",
 "revisions": []
}