---
title: "Prospect Medical Holdings security incident"
description: "What the retained public evidence establishes about the Prospect Medical Holdings incident, its attack path, impact, and response."
incident_type: "Cybersecurity incident"
status: "active"
last_modified: "2026-09-19"
canonical_url: "https://www.ally.security/incidents/prospect-medical-holdings-security-incident-2023"
markdown_url: "https://www.ally.security/incidents/prospect-medical-holdings-security-incident-2023.md"
stix_url: "https://www.ally.security/incidents/prospect-medical-holdings-security-incident-2023/stix.json"
---

# Prospect Medical Holdings security incident

The reviewed public source documents a cybersecurity incident involving Prospect Medical Holdings, while leaving material details unresolved.

Last modified Sep 19, 2026 · 1 source

## Summary

- **Environment:** Hospital system (16 hospitals)
- **Operational impact:** The reviewed source does not establish a precise operational or data impact
- **Financial impact:** No financial figure is established by the reviewed source evidence

## What happened

The reviewed public record documents a cybersecurity incident involving Prospect Medical Holdings in 2023. It does not establish the initial access path with enough specificity to describe it here. [1](#source-1)

## Impact

- The reviewed source does not establish a precise affected-person count, data scope, or operational consequence.
- No financial loss, ransom amount, recovery cost, or regulatory penalty is established by the reviewed source evidence.

## Timeline

### September 29, 2023 — Documented public update

The [Submitted Breach Notification Sample: Prospect Medical Holdings, Inc.](https://oag.ca.gov/ecrime/databreach/reports/sb24-574490) records the incident facts used in this briefing. [1](#source-1)

### September 19, 2026 — Briefing updated

This briefing was last reviewed and updated on September 19, 2026.

## Threat Group & Attack Vector

The reviewed source does not establish a sufficiently specific initial-access vector. The article therefore does not infer credentials, malware, a vulnerability, or a social-engineering path.

### Actors

- No threat actor group has been identified in the reviewed public evidence.

### TTPs

- No specific MITRE ATT\&CK technique is currently mapped for this case.

## Response

The reviewed source does not describe containment, notification, or restoration steps in enough detail to summarize them responsibly.

This account is bounded to [Submitted Breach Notification Sample: Prospect Medical Holdings, Inc.](https://oag.ca.gov/ecrime/databreach/reports/sb24-574490). Details absent from that evidence are left unresolved rather than inferred. [1](#source-1)

## Assets

[Download the case-scoped STIX 2.1 bundle](<https://www.ally.security/incidents/prospect-medical-holdings-security-incident-2023/stix.json>)

## Sources

Primary source records used to research this incident.

<a id="source-1"></a>

### Submitted Breach Notification Sample: Prospect Medical Holdings, Inc.

regulatory · California Department of Justice

<https://oag.ca.gov/ecrime/databreach/reports/sb24-574490>

<details>
<summary>Evidence ledger</summary>

Review the supporting structured claims.

1. **Resulted In · 100% confidence · current**  
   Prospect Medical Holdings security incident: The reviewed source documents the prospect medical holdings security incident involving Prospect Medical Holdings.
2. **Affected Organization · 100% confidence · current**  
   Prospect Medical Holdings security incident: Prospect Medical Holdings
3. **Occurred At · 100% confidence · current**  
   Documented public update: 2023-09-29

</details>