Google: This Spectre proof-of-concept shows how dangerous these attacks can be Google issues a new warning about Spectre attacks using JavaScript to leak data from one site to another. March 15, 2021 -- 11:27 GMT (04:27 PDT) | Topic: Security Google has released a proof of concept (PoC) code to demonstrate the practicality of Spectre side-channel attacks against a browser's JavaScript engine to leak information from its memory. Google in 2018 detailed two variants of Spectre, one of which – dubbed variant 1 (CVE-2017-5753) – concerned Javascript exploitation against browsers. Spectre targeted the process in modern CPUs called speculative execution to leak secrets such as passwords from one site to another malicious site.