Signals · Hot · first seen October 30, 2026
Tampered Claude Code add-on in Cursor's store planted an attacker's SSH key on developer computers
On Oct. 29, from about 2:27 a.m. to 1:35 p.m. Pacific, Cursor's extension store served tampered copies of the Claude Code add-on, versions 2.1.312 and 2.1.313. The added code collected machine details, added an attacker's SSH key and tried to open remote access, which Cursor says failed on most Windows and Mac machines. Microsoft says the official VS Code Marketplace and npm were not affected, and Anthropic told Microsoft its systems were not breached.
Why it matters to a business like yours
If a staff member or contractor writes code for you in Cursor, their laptop may hold the logins to your website, customer data or cloud accounts. Ask them to check for an SSH key named svc-telemetry, and if it is there, follow Cursor's cleanup steps and change the passwords that machine could reach.
Sources
- Security notice: malicious version of Anthropic.claude-code (2.1.312 and 2.1.313) identified in the Cursor VS Code Extension Marketplace (Cursor, October 29, 2026)
- Inside a malicious Claude Code-branded extension and its persistent SSH backdoor (Microsoft Security Blog, October 30, 2026)
- Malicious Claude Code extension on Cursor planted SSH backdoors (BleepingComputer, October 30, 2026)
On the Insider
- A fake Claude Code add-on sat in Cursor's store for about half a day (October 31, 2026)
History
- October 31, 2026: Hot