Cursor, the coding-tool company owned by SpaceX, informed that a maliciously modified version of Anthropic’s Claude Code extension was available in its Cursor VS Code extension marketplace from about 2:27 a.m. PT to 1:35 p.m. PT on Thursday. The incident has potentially affected up to 5,000 users.
Cursor disclosed the news on Friday, October 30, clarifying the modified extension was not developed by Anthropic.
Cursor noted that the malicious extension attempted to collect information about the host machine and its user. This included the device’s hostname, username, operating system, and public IP address.
The company also said the extension tried to establish remote access for the attacker. However, a key step in that process would have failed on most machines because it required administrator rights.
Cursor did not provide further details about how the extension was modified or whether any user data or systems were ultimately compromised. The figure of up to 5,000 refers to users who may have been affected by the availability of the malicious version.
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Cursor said it removed the malicious version after detecting the issue and blocked it from further distribution. As a precaution, it also shut down its extension marketplace.
The company subsequently rebuilt the marketplace and brought it back online. Cursor said the incident did not affect other extensions available through its marketplace.
The incident concerns a version of Anthropic’s extension distributed through Cursor’s marketplace. Cursor said the modified version was not developed by Anthropic. The claude-maker did not immediately respond to a request for comment, Reuters reported.
The company’s disclosure confirms the period during which the extension was available, the information it attempted to collect and the steps Cursor took in response. However, it does not establish how many users installed the modified version or whether attackers successfully gained remote access.
Cursor did not say whether the attempted remote-access process succeeded on any affected device or whether information sought by the extension was transmitted.