Anthropic's Claude Code extension was backdoored on Cursor for about 11 hours
Event Brief generated 48 s read
Written by an AI. It was merged from the 2 sources on this page and has not been reviewed by a person.
The short version
- A malicious Claude Code extension was distributed through Cursor's marketplace on October 29.
- Reports say it was available for about 11 to 12 hours and could reach up to 5,000 developers.
- It was designed to install persistent SSH backdoors. How attackers got into Anthropic's verified Cursor account is unknown.
What happened
A malicious version of Anthropic’s Claude Code VS Code extension was distributed through Cursor’s extension marketplace for about 11 hours on October 29, according to BleepingComputer. Ars Technica reports nearly 12 hours. BleepingComputer says up to 5,000 developers could have been exposed to malware designed to install persistent SSH backdoors. Ars Technica says it is still unknown how attackers got access to Anthropic’s verified Cursor account.
Why it might matter
Developers who installed the extension in that window may have SSH access held open by an attacker. Anyone who used Cursor’s marketplace that day should check for the extension and for unexpected SSH keys.
What we don’t know yet
The sources differ on the window (about 11 hours versus nearly 12). The number of affected installs is given only as an upper bound. The access path to Anthropic’s Cursor account is not known.
