Information for over 6,000 Memorial Hermann patients accessed in security breach. A contracted vendor with Memorial Hermann is looking into the security breach. Hackers could access social security numbers, financial information and more. HOUSTON — The Memorial Hermann Health System is notifying patients of a cyberattack that could impact thousands. One of their contracted vendors, Advent Health Partners , announced a cybersecurity issue Tuesday. According to the health system, the protected health information (PHI) for 6,260 patients have been breached. Third-party company: Advent Health Partners.