Computers are stupid, but what makes them useful is that they are stupid really quickly. The technology world was shaken by the disclosure of two vulnerabilities in modern processors: Meltdown and Spectre. The outcome for both vulnerabilities is the same a non-privileged user can access information on the computer they should not be able to, like secret keys or passwords. This is a particularly big problem for cloud services like AWS, where multiple tenants use the same physical hardware. The vulnerability relies on the assumption that users in one virtual machine cannot access data from another.”]
Source: https://stratechery.com/2018/meltdown-spectre-and-the-state-of-technology/