A request to access cookies or storage was partitioned because it came from a third party (a different origin) and dynamic state partitioning is enabled.
Firefox:
CookiePartitionedForeign=Partitioned cookie or storage access was provided to "<URL>" because it is loaded in the third-party context and storage partitioning is enabled.
With Dynamic State Partitioning enabled, Firefox provides embedded resources with a separate storage bucket for every top-level website. Embedded third-parties may request access to the top-level storage bucket via the Storage Access API. You can also disable Dynamic State Partitioning with the network.cookie.cookieBehavior pref.