Zero Radar
← feed
CriticalSecurity incidentupdated 30 Oct 2026, 14:47 UTC

Fake Claude Code extension on Cursor marketplace installed SSH backdoors

A fake copy of a popular AI coding helper was available for about 11 hours and could quietly give attackers secret remote access to developers' computers. Anyone who installed it may need to clean up their machine and check their SSH keys.

Attacks reported (r/netsec, Hacker News)1 source, unconfirmed
SeverityCriticalSecurity incident
Being exploited?ReportedBy r/netsec, Hacker News, BleepingComputer, not officially confirmed yet
What to doCheck exposureRemove the suspicious Claude Code extension from Cursor and check your machine for unknown SSH keys.
How sure is this?1 source, unconfirmedOnly one publisher so far, details may change

How the attack works simplified

  1. 1Attacker publishes fakeMalicious copy of the extension uploaded
  2. 2Cursor marketplace listingFake extension available for about 11 hours
  3. 3Developer installs itInstall happens through normal extension flow
  4. 4Backdoor installedPersistent SSH access added to the system
  5. 5Attacker gains accessRemote SSH login possible at any time
  6. ResultAttacker has persistent SSH access to developers' machines

What happened

A malicious version of Anthropic's Claude Code VS Code extension was distributed through Cursor's extension marketplace for roughly 11 hours on October 29, and was designed to install persistent SSH backdoors.

Why it is dangerous: Attackers with SSH backdoors can log into a developer's machine at any time, potentially reaching source code, credentials, and company systems. Up to 5,000 developers may have been exposed.

Are you affected?

You are affected if you installed a version of the Claude Code VS Code extension from the Cursor extension marketplace on or around October 29, 2026.

Malicious Claude Code VS Code extension distributed via the Cursor extension marketplace on October 29, 2026 (approximately 11-hour window).

What to do

  1. Check whether the Claude Code extension was installed from Cursor's marketplace on October 29, 2026, and remove it if so
  2. Review ~/.ssh/authorized_keys and SSH configs for unknown keys, and rotate any SSH keys and credentials that may have been exposed
  3. Install the extension only from the official publisher's verified source

Timeline

  1. 30 Oct 2026, 07:09 UTC
    Publicly disclosed
  2. 30 Oct 2026, 07:09 UTC
    Reported by Hacker News · Hacker News
  3. 30 Oct 2026, 12:41 UTC
    Reported by r/netsec · r/netsec
  4. 30 Oct 2026, 12:42 UTC
    Picked up by Zero Radar
  5. 30 Oct 2026, 14:35 UTC
    Hacker News reported on it · Hacker News
  6. 30 Oct 2026, 14:37 UTC
    BleepingComputer reported on it · BleepingComputer
  7. 30 Oct 2026, 14:37 UTC
    Reported by BleepingComputer

Sources 4 reports, oldest first

Security press established security newsrooms

Community discussion sites, treat with care

Technical details

ID
ZR-c423afe4
Disclosed
30 Oct 2026, 07:09 UTC
On Zero Radar
30 Oct 2026, 12:42 UTC (6 h after disclosure)
Last change
30 Oct 2026, 14:47 UTC

The plain-language parts and the attack diagram were written by an AI model (anthropic/claude-haiku-5.5) from the sources above. Facts like versions, exploitation and dates come from the sources themselves. How Zero Radar works

Fake Claude Code extension on Cursor marketplace installed SSH backdoors · Zero Radar