https://arstechnica.com/information-technology/2019/08/silent-windows-update-patched-side-channel-that-leaked-data-from-intel-cpus/

Microsoft last month pushed a silent update that mitigated a serious vulnerability in all CPUs Intel has introduced since 2012, researchers who discovered the flaw said Tuesday.

The vulnerability—discovered and privately reported to Intel 12 months ago—resided in every CPU Intel has introduced since at least its Ivy Bridge line of processors and possibly earlier, a researcher from security firm Bitdefender told Ars. By abusing a performance capability known as speculative execution, attackers could open a side channel that leaks encryption keys, passwords, private conversations, and other secrets that are normally off limits.