Marlborough Partners, a UK-based investment banking and advisory firm, was subject to a ransomware attack by the coinbasecartel group. This incident, which occurred on August 25, 2025, led to the exfiltration of 1 TB of data. The company discovered the breach on April 8, 2026. However, detailed information regarding the specific types of data compromised, the number of individuals affected, or whether personal information like SSNs, medical, or financial data was involved, has not been publicly detailed.
As of early 2026, no official breach notification statements from Marlborough Partners or regulatory filings have been found. The number of affected individuals and any specific data types beyond