A growing number of reliable sources (like Intel, Apple Support, Azure Blog, Amazon, Red Hat, Xen, among many others) provide details regarding major security vulnerabilities that affect modern microprocessors, and two specific exploits, called Meltdown & Spectre.

Meltdown dissolves the barriers between user applications and the operating system; This allows a program to access the memory of other programs and the operating system.

Spectre breaks the isolation between different applications on a system, allowing even well-designed programs that operate without error to leak their secrets.

Such exploits would likely include passwords or sensitive data held in memory.