John Muir Health - Walnut Creek Medical Center

John Muir Health - Walnut Creek Medical Center notified California AG on Apr 13, 2023 of a data breach, which occurred on Mar 24, 2023. Data exposed: Social Security number, Financial / bank account, Medical / health information, Phone number, Postal address, Name.

Case file (dates, days to notice against the statute, what the letter offers, prior incidents)

Organization: John Muir Health - Walnut Creek Medical Center
Source: California AG · source record
Date reported: Apr 13, 2023
Date(s) of breach: Thursday, July 1, 2021Friday, March 24, 2023
Residents affected: Not published by this source
Data exposed: Social Security number Financial / bank account Medical / health information Phone number Postal address Name
Notice letter: Sample notice (PDF)
Discovered: Mar 22, 2023, as stated in the letter
"Background On March 22, 2023, the John Muir Health (“JMH”) Privacy Office was notified that in an effort to facilitate more efficient communication among staff about use of certain medical devices, a staff member at the JMH Walnut Creek ..."
Days to notice: 22 days from discovery (Mar 22, 2023) to the California record (Apr 13, 2023). Statute: 30 days from discovery or notification of the breach (Cal. Civ. Code § 1798.82).
Third party: The letter attributes the incident to a vendor or service provider
First seen by BreachTally: 2026-10-30 15:59 UTC

Dates and counts as filed by the organization with the agency. The breach window and the report date often differ by months.

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Data reproduced from a public government filing. Spot an error? Email support@breachtally.com with the record link. Corrections are applied and noted.