Blockchain data provider Allium has disclosed a security breach involving unauthorized access to its systems. The company has not yet revealed how the intrusion occurred or what specific data was accessed, but confirmed that major clients including Visa, Coinbase, and KPMG rely on its services. Allium revoked all existing API keys on Oct. 28 as an immediate containment measure. The company is conducting an investigation with support from an external cybersecurity firm and plans to publish a summary of findings once the inquiry concludes.