Should origin-isolation inherit into blob: URLs?

[domenic]

Currently, if an origin uses the Origin-Isolation header to origin-isolate itself, and then creates a blob: URL, that blob: URL does not inherit the origin isolation state.

Now, the blob: URL is same-origin, so if the blob: URL is used for an iframe (which is within the same browsing context group), then the iframe will still be origin-isolated, because of the general consistency guarantee the spec enforces.

But if the blob: URL is used for a new browsing context group, e.g. via <a href="<the blob URL>" target="_blank">, then the new browsing context group will not be origin isolated.

This currently-specified behavior makes some sense to me. BCGs are very separate entities, and inheriting across them seems strange. However, it seems like some folks are surprised by this, e.g. in https://crbug.com/1151223. And #5198 discusses inheriting COOP for blob: URLs in similar situations, if I understand it correctly.

From what I understand, there is some general hope to uniformize the inheritance story for blob: URLs and others per #4926, so we probably want to stay consistent with the latest thinking there.

So, should we change anything here?

[annevk]

I would not see this as inheritance (at least not if we manage to pull of w3c/FileAPI#142), but rather state that's tied to the blob store when the blob URL got created. In this case, that state would cause an origin-isolated agent cluster to be created.