The company was forced to issue a statement after prominent figures in the cybersecurity industry alleged that the extension, which infected up to 5,000 developers, was uploaded to Cursor’s marketplace following a breach at Claudemaker Towers. Felix Rieseberg, a member of Anthropic’s technical staff, Xeeted today: "We're working with Cursor on this incident, but it wasn’t a compromise of Anthropic's systems or employee laptops. "A malicious actor used access to Cursor's marketplace to publish a tampered copy of the Claude Code extension, which we didn't build or publish.
The versions on our official channels are not affected, and this only impacts Cursor users." First spotted by EDR vendor Phorion, an unknown party pushed an update to Cursor's official Claude Code extension for Visual Studio Code that contained a persistent SSH backdoor written for Windows, macOS, and Linux. According to Cursor, the extension – version 2.1.313 – was available to download for around 11 hours between 0227 and 1335 PT (0927 and 2035 UTC) on Thursday.
