Fireworks AI says hackers accessed customer datasets and model weights

Fireworks AI said on November 9, 2026 that hackers accessed some customers' datasets, incomplete model weights and billing information, expanding an October security disclosure. The company says payment cards were not stored or impacted, and it has not detected impact to Inference, Training SDK or Nexus.

In that security bulletin, Fireworks updated its October 9, 2026 notice. After the earlier incident, it said, investigators found impacts to account and billing information, and for a limited set of accounts also to secrets, datasets and incomplete models. A third-party cloud provider that hosted Fireworks research-and-development machines had a security incident on October 23; on October 24 an unauthorized party used that path to reach Fireworks development machines and run an unauthorized workload that led to further customer-data impact, according to the company. Fireworks said it detected that activity the same day, and that as of October 25 it had not detected further successful unauthorized access on the platform customers use. Evidence, it said, links the activity to a financially motivated group aimed at selling unauthorized LLM access through illicit routing gateways, a pattern known as LLMJacking. Fireworks notified law enforcement and is working with Palo Alto Networks Unit 42. Billing data in scope included addresses, invoice and payment history, account balances and credit usage; Fireworks does not store payment card numbers. Self-serve dataset uploads and downloads used by Batch Inference and dataset-based training are disabled while the investigation continues, the bulletin says. Training SDK remains available with zero data retention, and Fireworks Lab-based training operates in an isolated environment with added network and storage protection, per the company.

Bloomberg described the November disclosure as Fireworks' second known hack in weeks. The Information reported that Fireworks had told large customers, including legal AI company Harvey, about a more serious recent hack. Forbes spoke with two customers who said they had already substantially moved business off Fireworks' systems; one described a series of "very bad hacks" and criticized Fireworks' customer communications. Two other customers told Forbes they were not aware of any Fireworks hacks. Forbes separately estimates Fireworks has about 10,000 enterprise customers, booked about $250 million in 2025 revenue, and reached a $17.5 billion valuation, figures it also used in an October 6, 2026 feature. Builders who keep sensitive training data and unfinished model assets on third-party platforms face the same trade-offs Codema covers in owning your code and data and in MCP security best practices. Fireworks' findings remain based on its investigation to date, the company said, and the inquiry is ongoing.