Malicious version of Claude Code discovered on Cursor marketplace
A malicious version of the Claude Code extension has been identified on the Cursor extension marketplace. The compromised versions contained backdoors designed to exfiltrate data from developers' machines.

What happened?
A malicious version of the Claude Code extension (Anthropic.claude-code versions 2.1.312 and 2.1.313) was detected on the Cursor code editor marketplace. The manipulated versions targeted Windows and MacOS systems and contained code engineered to harvest information from infected machines. The incident led to the prompt removal of the extension from the Cursor store.
Key facts
| Påverkade versioner | 2.1.312 och 2.1.313 |
|---|---|
| Berörda operativsystem | Windows och MacOS |
| Drabbad plattform | Cursor Extension Marketplace |
Why it matters
The attack highlights vulnerabilities in the software supply chain surrounding developer tools and extensions. As developers increasingly rely on AI assistants, compromised extensions can provide attackers with direct access to development environments, credentials, and proprietary source code.
Who is affected?
Developers and engineers using Cursor who installed the affected versions of Claude Code are directly impacted. Organisations whose programmers work with sensitive source code or store API keys locally are also affected from a security perspective.
Impact on the EU
The incident potentially affects developers within the EU who downloaded the extension via the Cursor marketplace. Development teams within the union are advised to conduct an inventory of their development environments and rotate API keys to prevent data leakage.
What else you should know
Cursor removed the malicious versions from its marketplace following the discovery of the incident. The team behind Cursor has published a security advisory recommending that affected users delete the extension and conduct a system review.
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