A maliciously modified version (2.1.313) of the Claude Code extension was distributed through the Cursor code editor's extension marketplace for about 11 hours on 29 October, exposing up to 5,000 developers, BleepingComputer reports. The added code collected system details, added an attacker SSH key and tried to open a reverse tunnel with persistence on macOS and Windows. Researchers say coding errors blocked access on many machines where SSH was not already running. Anthropic says it did not build the package.

What it means: Code editor extensions run with the developer's own rights and load automatically, so a tampered package with a familiar name is enough to reach the machine that holds cloud keys, repository access and production credentials. That the attack partly failed because of programming mistakes is luck, not defence. Even where the tunnel never opened, a foreign SSH key stayed installed and the attacker received the names of environment variables that show which secrets exist on the machine. For Greek development teams using Cursor or VS Code, the immediate steps are to check whether that version was installed, clean the authorized_keys file, look for unknown LaunchAgents or scheduled tasks, and rotate any keys that lived on the machine. In the longer run, teams need an allow-list of approved extensions, pinned versions where possible and a clear separation between developer laptops and production keys. The episode also shows that third-party extension marketplaces, which mirror packages from elsewhere, are a weak link in the software supply chain.

Read the original on BleepingComputer

Related service: Custom software

Related stories