Google: How to make any AMD Zen CPU always generate 4 as a random number

Malicious microcode vulnerability discovered, fixes rolling out for Epycs at least

Googlers have not only figured out how to break AMD's security – allowing them to load unofficial microcode into its processors to modify the silicon's behavior as they wish – but also demonstrated this by producing a microcode patch that makes the chips always output 4 when asked for a random number.…