PhantomPhreak

For years we’ve been reading about how vulnerable so many computer systems, especially ones using Intel and AMD processors, are highly vulnerable to speculative execution attacks such as Spectre, Meltdown, Foreshadow and Fallout. Numerous demonstrations of the feasibility of these attacks have been published, seemingly showing their practicality (even in JavaScript). Microcode updates that partially mitigate them have meant significant performance slowdowns, also suggesting their practicality. Are there many cases where these vulnerabilities have led to actual security breaches of real-world systems?