Source: stepsecurity.io
On October 29, 2026, version 2.1.313 of the official Claude Code VS Code extension (anthropic.claude-code) was published with a malicious loader embedded in its extension.js bundle. The trojanized version was distributed via the Open-VSX registry and Cursor's extension marketplace, reaching up to 5,000 Cursor users during an 11-hour window. Upon loading, the extension planted an attacker-controlled SSH key on the victim machine, installed OS-specific persistence mechanisms, and opened a reverse SSH tunnel to attacker-controlled infrastructure. Additionally, the malware beaconed host reconnaissance data over plain HTTP. The attack represents a supply chain compromise targeting developer machines through a trusted IDE extension. StepSecurity verified the payload behavior through sandbox and independent registry analysis. The incident highlights risks in mirrored extension marketplaces where malicious versions can propagate quickly.
