Dormant High impact Data breach Checked 2d ago

MCBS breach affects 1.26 million people

Attackers entered medical billing company MCBS and may have stolen files holding personal, insurance, and medical information. The breach affected 1,261,464 people whose data came from seven healthcare providers.

Started
Sep 22, 2025
Latest activity
Aug 21, 2026
Attributed to
PEARConfirmed
Where
United States
Sectors
Healthcare
Scale
MCBS and seven healthcare provider clients

Current status

On August 21, 2026, Law360 reported that patients dropped a lawsuit against MCBS; no newer credible incident activity or official closure was found.

Dormant: No new confirmed activity for a while, and nobody has called an official all clear.

Who is behind it

No newer government, victim, or agency statement changed the reported PEAR claim.

Impact

Files may have exposed names, addresses, Social Security numbers, insurance details, medical histories, treatments, and diagnoses. MCBS said it had no evidence of related identity theft.

What to do

People who receive an MCBS notice should place a free fraud alert or credit freeze and check financial and insurance statements for misuse.

Timeline

  1. Aug 21, 2026

    A group of patients dropped a lawsuit accusing MCBS of failing to properly secure patients' personal information.

    Dormantlaw360.com
  2. Aug 11, 2026

    No new confirmed activity reported, so this incident moved to dormant while it stays open.

    Dormant
  3. Jul 29, 2026

    Reporting put the affected population at 1,261,464 and said PEAR had claimed responsibility.

    Containedesecurityplanet.com
  4. May 28, 2026

    MCBS determined that affected files may have held personal, insurance, and medical information.

    Containedmcbs.com
  5. Sep 26, 2025

    MCBS later determined that the access and possible file theft window ended on September 26.

    Containedmcbs.com
  6. Sep 25, 2025

    MCBS detected unauthorized activity around September 25 and said it immediately contained the incident.

    Containedmcbs.com
  7. Sep 22, 2025

    MCBS said unauthorized access to its network began on September 22.

    Activemcbs.com

Sources

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