To prevent unintended clicks/taps, quietly discard input events that target cross-origin iframes that have recently resized or moved a non-trivial distance within the embedding page's viewport. The shipped version limits the intervention to cross-origin iframes that are using the V2 feature set of IntersectionObserver (https://github.com/w3c/IntersectionObserver/tree/v2).
The motivation is perhaps best conveyed by this hilarious video: https://www.youtube.com/watch?v=3tUmh8OfAiY We would like to prevent untrustworthy embedders from using visual bait-and-switch tactics to induce users to click or tap on a third-party iframe.
Docs: https://docs.google.com/document/d/1qzgHiruzTvt0_-rfe7suZRCe2KhSJxiBp28ZTLd9Xls/edit?usp=sharing
Explainers: https://docs.google.com/document/d/1AL9RMFxLRRTQ818Bi7RPjbxF5JPBhti8XWNbLg83LYE/edit?usp=sharing