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Cursor says up to 5,000 users affected by tampered Claude Code extension

By Thomson Reuters Oct 30, 2026 | 3:32 AM

Oct 30 (Reuters) – Cursor, the coding-tool company owned by SpaceX, said on Friday that a maliciously modified ​version of Anthropic’s Claude Code ‌extension was available on its Cursor VS Code extension marketplace on Thursday, affecting up to 5,000 users.

Here are some details:

• Cursor ‌said ​the extension was not ⁠developed by Anthropic ⁠and the maliciously modified extension was live on the marketplace from about 2:27 a.m. PT to 1:35 p.m. PT ​on Thursday

• The extension attempted to collect host and user information ⁠such as hostname, ⁠username, operating system and public ​IP address

• It also attempted to set ​up remote access for the attacker; ‌Cursor said a key step would have failed on most machines because it requires administrator rights

• Upon detection, ⁠Cursor removed the malicious version and blocked its distribution and shut down the marketplace as ⁠a precaution

• ‌The company then rebuilt ⁠the marketplace and brought it ​back ‌online, it said

• Cursor said ​the incident ⁠did not impact other extensions on its marketplace

• Anthropic did not immediately respond to a request for comment

(Reporting by Shubham Kalia in Bengaluru; Editing by ​Mrigank Dhaniwala)