Anthropic says a malicious actor used access to Cursor's marketplace to publish a "tampered" copy of the Claude Code extension, which it didn't build or publish (Felix Rieseberg/@felixrieseberg)

Anthropic reported that a malicious actor used access to Cursor’s marketplace to publish a tampered copy of the Claude Code extension. Techmeme reports that the company is working with Cursor on the incident but noted it was not a compromise of Anthropic’s employee laptops or internal systems.

Ars Technica reports the compromised VS Code extension was version 2.1.313, which was distributed through Anthropic's official account on Cursor. This version may have affected at most 5,000 users through manual downloads or automatic updates. Luke Roberts, the CTO and co-founder of security firm Phorian, described the event to Ars Technica as a supply-chain compromise where the attacker gained access to the official distribution channel. Neither Cursor nor Anthropic has explained how the account was accessed.

In separate news, Anthropic has updated its pricing and usage policies. The New Stack reports that Claude Code users on the $200 "Ultra" plan—formerly known as Max 20x—will no longer face a rolling five-hour usage cap, provided their accounts are verified. Additionally, Dev.to reports that Anthropic added a server-side rule to Claude Code for the Opus 5.5 model to prevent it from recreating specific existing games, a move Anthropic technical staff member Addy Osmani stated was intended to avoid IP infringement.

Brief written by urgent.news from Techmeme, Dev.to, Ars Technica, The New Stack, Dark Reading — 5 reports on this story. Machine-written — may contain errors; check the original before relying on it.