A vendor’s breach becomes a business crisis: Lessons from the Cierant Data breach

**Cierant data breach (Dec 2024–2025):** Cierant Corporation suffered a vendor‑origin breach after attackers exploited a vulnerability in Cleo VLTrader, exposing protected health information for 232,506 individuals, prompting consolidated class‑action litigation and regulatory notification; the report summarizes the incident timeline, legal exposure, and vendor‑risk remediation guidance for CISOs.