Top-level sites and Clear-Site-Data

[DCtheTall]

At the time of writing this, the explainer currently states that browsers give top-level sites the ability to clear third parties' cookies by sending a Clear-Site-Data header.

In other words, say example[1-10].com set cookies under toplevel.com's partition. Then toplevel.com could send a Clear-Site-Data header in a response which would clear all of example[1-10].com's cookies in the toplevel.com partition.

I am opening this issue because I am less convinced that this is functionality is either necessary or a good idea.

@annevk mentioned in the storage partitioning repo that this could allow malicious first parties to interfere with code running on third-party frames.