Cursor Says Stolen Fireworks AI Key Led to Trojanized Claude Code Extension Incident
Summary: Cursor said an attacker obtained an access key it had issued to Fireworks AI, which Fireworks exposed, and used it to copy data from a read-only storage bucket containing coding agent traces from sessions not in Privacy Mode, including unredacted API credentials for less than 0.01% of customers. On October 29, 2026, the attacker used a stolen credential from that data to place trojanized versions of Anthropic's Claude Code extension on the cache serving Cursor's marketplace, where versions 2.1.312 or 2.1.313 were available for about 11 hours and potentially reached at most 5,000 users who requested specific cached versions.
Key Takeaway: A single vendor's exposed access key led to a trojanized extension reaching up to 5,000 developers through a trusted marketplace, and the same Fireworks AI breach is tied to data theft at Uber and Notion.
Read the original at The Hacker News ↗