Spectre and Meltdown proved that even chips can have backdoors. It’s not some absolute backdoor that guarantee certain access, but it contributes to the overall security of the system, making it more susceptible to attacks.

I wonder how many zero-day security vulnerabilities were there by human negligence, how many were intentionally installed. I do know that there is an Israel business (forgot the name) who specializes in selling exploits of unpatched zero-day vulnerabilities to Western spy agencies.