Every public data breach

Disclosed this week44On record26,355

44 disclosed this week · 26,355 on record

MCBS

Disclosed Jun 26, 20261,261,464 affectedConfirmed

Official notice

What is known

People affected1,261,464 (as reported to HHS)
DisclosedJun 26, 2026
DiscoveredMay 28, 2026
HappenedSep 22, 2025
AttackHacking
Data exposedNamesHealthSocial Security numbersInsuranceDates of birthAddresses
SectorHealthcare · US
StatusConfirmed

Sources

Official noticeoag.ca.gov
California Attorney General breach notice: MCBS
Official noticeocrportal.hhs.gov
HHS OCR breach report: MCBS (Business Associate, GA)
Official noticeoag.my.site.com
Texas Attorney General data security breach report BR-0005146: MCBS

Notices filed

Residents of CAJun 26
California AGCount not stated
TotalJun 26
HHS OCR1,261,464 people
Residents of TXJun 30
Texas AG13,302 people
History of this record
data_types2026-09-25
["names","health"] to ["names","health","ssn","insurance","dob","addresses"]by backfillSource
discovered2026-09-25
empty to 2026-05-28by backfillSource
sector2026-09-25
other to healthby backfillSource
attack2026-09-25
unknown to hackingby backfillSource
data_types2026-09-25
[] to ["names","health"]by backfillSource
records_basis2026-09-25
empty to hhsby backfillSource
records2026-09-25
empty to 1261464by backfillSource
Added2026-09-25
First recordedby backfillSource

First seen 2026-09-25 (California AG), confirmed by California AG. Record counts are as reported. Not legal advice.

Everything about MCBS