Spectre was shown to be exploitable from Javascipt: https://www.zdnet.com/article/google-this-spectre-proof-of-concept-shows-how-dangerous-these-attacks-can-be/

Spectre was shown to be exploitable from Javascipt: https://www.zdnet.com/article/google-this-spectre-proof-of-concept-shows-how-dangerous-these-attacks-can-be/ https://www.zdnet.com/article/google-this-spectre-proof-of-c... - making the bet that this won't be shown the same is not a safe wager I would say :) (especially that Javascript also includes stuff like WebAssembly).