“It is unclear how exactly Microsoft fixed the vulnerability, and what mitigation recommendations were implemented.”
A poisoned email or document made Microsoft 365 Copilot hide stolen data in invisible Unicode characters inside a link. Microsoft closed the first report on January 18, 2024 as low severity. A full exploit that pulled sales data arrived in February, and Microsoft then asked for until the end of May to fix it. The prompt injection still works. The links stopped rendering, and Microsoft never said what it changed.