Do we also partition b/w multiple embedded frames having the origin?

[vardhman-singh-glean]

As in the title - i've observed that in recent Chrome release - Version 131.0.6778.109 (Official Build) (arm64), frames are getting partitioned even if they belong to the same origin as each other. Previously, the frames would get partitioned, but still be able to share state if 2 of them were embedded in the same site.

[miketaylr]

Hey @vardhman-singh-glean - thanks for the issue. Just to clarify, it sounds like you're describing the following:

https://a.com, embeds 2 iframes, each with the origin https://b.com and https://b.com.

And your expected behavior would be that one b.com iframe setting state somehow would be readable by the other b.com iframe, yes?

Would you happen to have a minimal test case to reproduce this (glitch.com is pretty good for setting up simple demos)?