Marshfield Clinic Health System reports email account compromise exposing patient data
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Marshfield Clinic Health System reports a data breach affecting patient information after a breach ofemployee email accounts in late August 2025.
The Wisconsin-based integrated health system detected unusual activity in certain employee email accounts on August 27, 2025 The investigation confirmed unauthorized access to employee email accounts between August 26 and August 27, 2025. The investigation confirmed that attackers potentially accessed sensitive patient information contained within email communications and attachments. The exposed data may include:
- Names
- Addresses
- Phone numbers
- Dates of birth
- Insurance ID numbers
- Medical record numbers
- Dates of service
- Treatment and diagnosis information
- Laboratory test results
- Medication information
The number of affected patients has not been disclosed.
Marshfield Clinic began notifying potentially affected patients in early November 2025 and is offering complimentary identity monitoring services to all affected individuals.
