For Attribution Reporting, the attributionsrc attribute was already unintentionally processed on <area> elements due to code shared with <a>, which intentionally supported that attribute. For completeness, we expose the attribute on <area> with identical syntax and semantics to <a> and without changing the previous processing: When an <area> tag with an attributionsrc attribute is navigated, the foreground request may register navigation sources and, if the attribute is non-empty, one or more background requests will likewise be able to register navigation sources.
This aligns exposure of the attribute on <area> with the existing processing behavior of the attribute, even when it wasn't exposed. Additionally, it makes sense to support the attribute on <area> anyway, as that element is a first-class navigation surface, and we already support this on the other surfaces of <a> and window.open.
Explainers: https://github.com/WICG/attribution-reporting-api/blob/main/EVENT.md#registering-attribution-sources