Quest Diagnostics

Cybersecurity incident disclosed to the SEC (8-K Item 8.01)

On October 21, 2026, Quest Diagnostics Incorporated (the "Company") learned of unauthorized access to its Quanum LSM system, which certain clients use to place test orders, receive and look up results. The Company promptly initiated its cybersecurity incident response procedures to contain the activity, assess and investigate the nature and scope of the incident and implement appropriate remedial measures. The Company has notified federal law enforcement authorities and engaged external cybersecurity experts to assist in the investigation and response. While the full scope of unauthorized acce