Malicious Claude Code extensions distributed through Cursor marketplace
Tampered versions 2.1.312 and 2.1.313 of the Claude Code extension were distributed through Cursor's extension marketplace for around 11 hours, potentially exposing up to 5,000 developers to malware. The malicious extensions transmitted host information and installed attacker SSH keys and persistence components or attempted to establish reverse SSH tunnels. Cursor removed the packages and temporarily suspended and rebuilt the marketplace. Cursor later confirmed that the malicious extensions had been distributed through a breach using credentials stolen from AI infrastructure provider Fireworks.
Key facts
- Affected organisation
- Cursor
- Incident type
- Malware
- Occurred / detected
- Not confirmed
- Scale of damage
- Up to 5,000 developers potentially exposed to malware
- Cause / method
- Breach of Cursor's marketplace using credentials stolen from Fireworks, followed by distribution of malicious extensions
- Location
- United States
Timeline
- Cursor announced the distribution of two malicious Claude Code extension versions, the removal of the packages and the rebuilding of its marketplace.
- Reports indicated that the malicious extensions may have exposed up to 5,000 developers to malware.
- The malicious code was reported to have attempted system reconnaissance and the creation of reverse SSH tunnels.
- Cursor confirmed that the malicious extensions had been distributed through a breach using credentials stolen from Fireworks.
5 related reports
- Security notice — malicious version of Anthropic.claude-code (2.1.312 and 2.1.313) identified in the Cursor VS Code Extension Marketplace
- Malicious Claude Code extension on Cursor planted SSH backdoors
- Malicious Claude Code Extension Served in Cursor Supply Chain Attack
- Malicious cPGuard Updates Served in OpsShield Supply Chain Attack
- Cursor confirms security breach led to malicious Claude Code extension
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The summary and key facts are written by AI from related reports and may contain errors. Check the original articles and the organisation’s official statements for accurate details.