HackingHealthcareTechnologyHealthcareVulnerability ExploitSupply Chain (3P Vendor)Customer Data InvolvedIdentity (basic)Government IDHealth (basic)PHIMediumContained

Blue Cross and Blue Shield of Massachusetts, Inc.

bd_249d2927c5e04cd8 · schema v1 · pii pii-v1

Severity

Medium

Discovered

Dec 10, 2024

Filed

Jul 7, 2025

To disclose

30 weeks

Affected

Not disclosed

Linked

2 filings

Confidence

66%

Full breach record for Blue Cross and Blue Shield of Massachusetts, Inc. →16 incidents on file

Cierant Corporation, a distributed marketing software vendor for Blue Cross and Blue Shield of Massachusetts, disclosed a data security event involving a vulnerability in the third-party file transfer tool Cleo VLTrader. An unauthorized actor exploited this vulnerability to gain limited access to Cierant systems, potentially acquiring files containing personal information of approximately 1,422 Rhode Island residents. The incident was discovered on December 10, 2024. Cierant ceased use of the tool, rotated passwords, and is offering credit monitoring.

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California clockDiscovered Dec 10, 2024 → Notified Jul 3, 2025205d ✗ CA 60-day late30 weeks discovery → filing

Incident timeline

undetected · 1 days

discovery → filing · 30 weeks / 209 days

Dec 9, 2024

Begins

Dec 10, 2024

Discovered

Jul 7, 2025

Filed

vs. sector median

+21 wks slower

This filing is one of 2 filings about the same incident.View merged incident

Part of Cleo supply-chain incident (2025) — a supply-chain cascade affecting multiple organizations.View cascade →

Linked disclosures

Why this link?

Regulatory filings (1) · sorted by filing gap

Montana State AGbd_154646e20b01c5db2025-07-07Candidate

Name: Cierant
norm: cierant
Domain: cierant.com

Name: Blue Cross and Blue Shield of Massachusetts, Inc.
norm: blue cross and blue shield of massachusetts
Industry: HealthcarellmTechnologyllm

Discovered: Dec 10, 2024
Breach occurred: Dec 9, 2024
Undetected for: 1 dayoccurrence → discovery
Materiality determined: —
Notification sent: Jul 3, 2025
Affected individuals: Not disclosed
Data types: Identity (basic)Government IDHealth (basic)PHI
Data elements: Social Security number
Attack vector: Third-Party / Supply Chain
MITRE ATT&CK: T1190 Exploit Public-Facing ApplicationT1195 Supply Chain Compromise
Threat actor: External
Regulator citations: Reported the event to federal law enforcementNotifying relevant regulators
Third party: via Cleo
Initial access: supply_chain

During the incident: Ceased use of Cleo VLTrader
Rotated passwords
Enhanced existing network security controls
Reported the event to federal law enforcement
Notifying relevant regulators
Offering 12 months of complimentary credit monitoring services through Epiq
Source: Quoted from the filing itself, not independently verified.

Time to disclose: 30 weeks(209 days from discovery to filing)
Compliance flags: CA 60-day late · 205d
Discovery-date grounding: letter-groundedThe discovery date is the detection date narrated in the notification letter — the defensible tier.
Clock breakdown: Statute Window Elapsed Threshold Status
California
Discovered: Dec 10, 2024
→ Notified: Jul 3, 2025
205d 60 days (analyst band, pre-2026 discoveries) CA 60-day late

Statute	Window	Elapsed	Threshold	Status
California	Discovered: Dec 10, 2024 → Notified: Jul 3, 2025	205d	60 days (analyst band, pre-2026 discoveries)	CA 60-day late

Status: No extraction artifact recorded for this disclosure.

Filing propagation · 2 filings · 2 states

View merged incident ↗

Montana State AGJul 7 · first

California State AGJul 7 · first · this page

Evidence ladder

Leak-site claim

Attacker assertion only. Establishes: claim date, group, alleged victim.

Press / market report

Unlocks: incident narrative, operational impact. Still no compliance clock.

State AG / regulator filingThis record

Unlocks: discovery date, data types, affected count, compliance clock.

SEC 8-K / victim statement

Unlocks: materiality, stated response, full audit trail. Ceiling removed.

Source URL: https://oag.ca.gov/ecrime/databreach/reports/sb24-605063
DisclosureLens links to the originating regulator URL — full filing bodies are not redistributed from public surfaces (§4.5).
Filed at: Jul 7, 2025
Raw hash: c89c176f20ee7c0c039a3d4bb3f8576677e2e404ffc6e92d237434b7a3f52ce0

Linked disclosures

Regulatory filings (1) · sorted by filing gap

Reporting entityCierant

Victim entityBlue Cross and Blue Shield of Massachusetts, Inc.

Incidentdiscovered Dec 10, 2024

Stated responseCeased use of Cleo VLTrader

ComplianceCA 60-day late

Extraction provenanceno artifact recorded

Source provenanceoag.ca.gov