On October 30, 2026, cybersecurity researchers identified a malicious update to Anthropic’s official Claude Code extension, distributed through Cursor Marketplace as a...
Cybersecurity researchers disclosed a trojanized version of Anthropic’s Claude Code extension was distributed through Cursor Marketplace as a legitimate update.
What changed
On October 30, 2026, cybersecurity researchers identified a malicious update to Anthropic’s official Claude Code extension, distributed through Cursor Marketplace as a legitimate update. The compromised version, labeled 2.1.313, was found to install a persistent SSH backdoor on affected systems. Cursor Marketplace temporarily suspended operations following the discovery, though the exact duration of the suspension was not confirmed.
What is confirmed
The malicious update, version 2.1.313, was distributed under the legitimate publisher identity of the Claude Code extension, making it indistinguishable from a genuine update. Cybersecurity researchers confirmed the presence of a persistent SSH backdoor, which could allow unauthorized remote access to compromised systems. The malicious package was discovered on Open VSX, an open-source marketplace for VS Code extensions, but no malicious versions were reported on Microsoft’s Visual Studio Marketplace. The extent of the breach’s reach remains unconfirmed, with no details provided on how many users were affected.
What to watch or do next
Users who installed the Claude Code extension from Cursor Marketplace should immediately check for updates and verify the authenticity of any new versions. Developers using VS Code-compatible editors are advised to review their extension installations and ensure they are sourced from trusted repositories. Cursor Marketplace has not yet announced a timeline for resuming operations or providing a detailed incident report.
Frequently Asked Questions
Q1: Which version of the Claude Code extension was compromised?
The malicious update was version 2.1.313.
Q2: Where was the malicious package discovered?
The malicious package was found on Open VSX, an open-source marketplace for VS Code extensions.
Q3: Is the Visual Studio Marketplace affected?
No malicious versions of the Claude Code extension were reported on Microsoft’s Visual Studio Marketplace.