Cursor says the October attack that put a backdoored Claude Code extension in its marketplace began with an access key exposed at its vendor, Fireworks AI. Separately, Uber confirmed this week that driver’s license data it had stored with Fireworks was stolen, and Notion has disclosed a related loss of AI chat transcripts. One breach at an AI vendor is now reaching several of its customers.
What happened
Fireworks AI, which lets developers run open AI models, published its first bulletin on October 9. At that point it knew of access only to secrets Fireworks itself stored. Its update of November 9 says investigators later found account and billing information was affected too, and for a limited set of accounts, secrets, datasets and incomplete models. Fireworks says payment card numbers are not stored and were not affected. It links the activity to a financially motivated group that sells access to stolen LLM capacity, a scheme known as LLMjacking. Fireworks also reports that a third-party cloud provider hosting its R&D machines had an incident on October 23, which the attacker used on October 24 to reach development machines.
On November 13, Cursor published its own account. It says an attacker obtained an access key Cursor had issued to Fireworks, and that Fireworks exposed it. The key gave read-only access to a shared bucket of coding-agent traces, mostly from 2025, from sessions not using Privacy Mode. A small number contained unredacted credentials. Using those, the attacker reached some of Cursor’s SaaS tools, including archived non-production source repositories and limited support data. On October 29, with a stolen credential, the attacker placed malicious copies of Anthropic’s Claude Code extension in the cache serving Cursor’s marketplace. Cursor says Anthropic did not publish them and its product was not vulnerable. The tampered versions, 2.1.312 and 2.1.313, were live for about 11 hours and reached at most 5,000 users. Cursor says the last attacker activity it saw, on November 1, was blocked.
Uber’s notices to state regulators, as reported by TechCrunch, say a vendor told Uber on October 9 that hackers had stolen internal credentials and used them to reach Uber data. TechCrunch identified the vendor as Fireworks, and Uber confirmed it. Filings list driver’s licenses for 2,567 people in Massachusetts, 3,430 in South Carolina and 1,873 in Rhode Island. Illinois lists an affected number as pending, and California has no count. Notion said the breach touched around 1% of its customers, exposing Notion AI chat transcripts from its Insights feature; it disconnected from Fireworks on November 3.
Who is affected
- Cursor users who installed or updated the Claude Code extension on October 29.
- Cursor users outside Privacy Mode whose old traces leaked: fewer than 0.05% of users, who Cursor says it notified directly.
- Fireworks customers who received a notification, and Uber drivers named in state filings.
- Some Notion AI users, though Notion says much of the data cannot be tied to a specific customer.
What to do
From Cursor: if you ran the tampered extension, follow the steps and check scripts in its October 29 security notice, because uninstalling alone may leave an attacker’s SSH key and startup scripts behind. Reporting names the key label as svc-telemetry. Rotate any credentials Cursor listed for your team.
Our analysis, not from the sources: treat any secret pasted into an AI coding session or a support email as exposed if the vendor was breached. Rotate it, and scope vendor keys to specific networks where possible. Fireworks customers should act on their notification email and review which datasets and secrets they shared. Uber drivers who get a notice should watch for identity misuse and consider a credit freeze. Uber said it had not identified misuse when it sent the letter, according to a secondary report.
What we still do not know
- Uber has not given a total count; the three states above add up to 7,870 by our arithmetic, and that is not the full figure.
- Fireworks has not said which of its systems held Uber’s data, and its bulletin does not name Cursor.
- No group has claimed the data theft, and Fireworks says its investigation is ongoing.
Sources: Cursor, An update on our recent security incident (Nov 13, 2026); Fireworks AI, Update on October 2026 security incident (updated Nov 9, 2026); TechCrunch, Uber confirms hackers stole thousands of drivers’ license information (Nov 13, 2026); TechCrunch, Fireworks AI attack and Notion transcripts (Nov 12, 2026); Cyber Security News, Cursor and Fireworks key (Nov 14, 2026).
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