The exploit was discovered by French security researcher Julien Voisin. Voisin's discovery is about as close the Spectre doomsday clock can tick close to midnight before attacks get underway, if they haven't already.
The Spectre bug is a hardware design flaw in the architectures of Intel, AMD, and ARM processors that allows code running inside bad apps to break the isolation between different applications at the CPU level and then steal sensitive data from other apps running on the same system.
https://therecord.media/first-fully-weaponized-spectre-exploit-discovered-online/