Backdoors found in official Claude Code extensions
The gist
A trojanized build of Anthropic's Claude Code VS Code extension reached up to 5,000 Cursor users.
The backdoor targets developer machines, which hold source code and credentials.
How it unfolded
- Oct 29, 2026Version 2.1.313 of the official extension anthropic.claude-code was published with a malicious loader embedded in its extension.js bundle, distributed through Open VSX and Cursor's mirroring marketplace.
- Oct 29, 2026 09:27 UTCStart of the window in which the trojanized build was installed; Cursor reports at most 5,000 of its users received it during an 11-hour window.
- Oct 30, 2026Anthropic removed the Open VSX release and pulled the NPM and VS Code versions of 2.1.313, and published 2.1.314.