Trojanized Claude Code extension on Cursor marketplace delivered SSH backdoor to developer machines
According to a Cursor security advisory, versions 2.1.312 and 2.1.313 of the Anthropic.claude-code extension were malicious on Cursor's VS Code marketplace. Reports say it tried to install a persistent SSH backdoor on developers' machines.
Who is affected and how
- senior developer
- Check whether anyone installed version 2.1.312 or 2.1.313; if so, treat the machine and its SSH keys as compromised.
- junior developer
- Install extensions only from verified publishers and pin them to a fixed version.
Sources
- Trojanized Claude Code Extension Delivered Persistent SSH Backdoor to Developer Machinesstep security · Oct 29, 2026
- Inside a malicious Claude Code-branded extension and its persistent SSH backdoormicrosoft · Oct 30, 2026
- Official Claude Code Extension on Cursor Marketplace Trojanized with Persistent SSH Backdoorthe hacker news · Oct 30, 2026
- Malicious Claude Code extension distributed through Cursor marketplacesophos · Oct 30, 2026
- Claude Code extension poisoned with persistent SSH backdoorhelp net security · Oct 30, 2026
- Malicious Claude Code extension on Cursor planted SSH backdoorsbleepingcomputer · Oct 30, 2026
- Trusted Tool, Malicious Build: What the Trojanized Claude Code Extension Means for Developer Endpointsmorphisec · Oct 30, 2026
- Malicious Claude Code extension in Cursor's marketplace attempted remote access and data theftthe decoder · Oct 30, 2026
Machine-generated summary based on the titles and excerpts of the source articles. The facts come from the linked article.