The Mozilla Hacks blog covers
some recent Firefox changes that will allow code from web sites to use
shared memory and high-resolution timers in a (hopefully) safe manner.
“Together with others in the WHATWG community, we designed a set of headers that meet these requirements.

The Cross-Origin-Opener-Policy header allows you to process-isolate
yourself from attackers. It also has the desirable effect that attackers
cannot have access to your global object if they were to open you in a
popup. This prevents XS-Leaks and various navigation attacks. Adopt this
header even if you have no intention of using shared memory!“

Source: LWN.net – Safely reviving shared memory (Mozilla Hacks)