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Cursor disclosed that a tampered Claude Code VS Code extension appeared in its IDE extension marketplace, affecting up to 5,000 users, and stated that the malicious version was not developed by Anthropic. Cursor took the extension marketplace offline the same day, worked with the relevant service providers to remove the malware, restored the marketplace after confirming there was no further risk, and required all users to upgrade to Claude Code for VS Code version 2.1.314. Subsequent reports said the tampered extension was version 2.1.313, went live on October 29 and remained available for about 11 hours, and may have been downloaded by up to 5,000 developers; the malware attempted to install a persistent SSH backdoor, collected the names of environment variables related to usernames, hostnames, public IP addresses, Git email addresses and sensitive credentials and sent them to an attacker-controlled server, and also added an attacker-controlled SSH key to achieve persistence. Cursor has taken down the extension and temporarily shut down the entire extension marketplace to review other plugins and rotate access keys, while working with its hosting provider to shut down the attacker's server, but it has not yet explained how the attacker published the tampered package under Anthropic's name.
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Oct 31
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Malicious Claude Code Plugin Appears in Cursor's Official Marketplace, Affecting About 5,000 Developers Over Roughly 11 Hours
Cursor's plugin marketplace listed a tampered Anthropic Claude Code extension on October 29, version number 2.1.313, for about 11 hours, with as many as 5,000 developers potentially downloading it. Cursor has confirmed that the malware attempted to install a persistent SSH backdoor, collected usernames, hostnames, public IP addresses, Git email addresses, and the names of environment variables related to sensitive credentials and sent them to the attacker's server, and also added an attacker-controlled SSH key to achieve persistence. Cursor has removed the extension and temporarily shut down the entire extension marketplace to review other plugins and rotate access keys, while coordinating with the hosting provider to shut down the attacker's server, but it has not yet explained how the attacker published the tampered software package under Anthropic's name.
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Oct 30
Solidot
Backdoor implanted in official Claude Code for VS Code extension on Cursor Marketplace
Security researchers discovered a backdoor in the official Claude Code for VS Code extension on Cursor Marketplace. The affected version is Anthropic.claude-code 2.1.313, which was online for about 11 hours and is estimated to have affected about 5,000 users. The malicious extension collects information such as hostname, username, operating system, environment variables, Git email, and public IP; attempts to add attacker-controlled SSH keys to authorized_keys, enable the local SSH service, and establish a reverse SSH tunnel; and also uses a LaunchAgent or scheduled task to keep the tunnel active long-term, retrying about once every 60 seconds. Due to a bug in the malicious code, the SSH key implantation step will fail unless Cursor is launched with administrator privileges. This version has been taken down, Cursor has published a security advisory, and Anthropic has not yet made a statement; users who installed or updated to this version between 2:27 AM and 1:35 PM Pacific Time on October 29, 2026 need to check their systems.
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CursorFirst-partySelected
Tampered Claude Code extension appears in Cursor extension marketplace, affecting up to 5,000 users
Cursor said that a tampered Claude Code VS Code extension appeared in its IDE extension marketplace, affecting up to 5,000 users; the malicious version was not developed by Anthropic. Cursor took down the extension marketplace the same day, worked with relevant service providers to remove the malware, and after confirming there was no further risk, restored it online and required all users to upgrade to Claude Code for VS Code version 2.1.314.
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