> "Taking this approach a step further, Safari follows a simple one process per tab model, where two web- pages are never consolidated into the same rendering process, even under high memory pressure and even if they share an eTLD+1 in their URLs. Instead, Safari spawns a new rendering process for each tab until the system runs out of memory."

This suggests that Safari/Webkit is even more hardened in general. It's only in the context of `window.open()` that this isolation strategy is defeated. Notably, `window.open()` somewhat implies a shared context between the calling window and the newly opened one, since both windows receive a direct reference to the respective other one. I can't see any description, how other browser engines would handle this differently and would achieve perfect isolation, or, in case these were explored in similar depth, might yield similar vulnerabilities.

Browsers with sandboxed multi-process architectures have been around since 2008, precisely because experts realised that rendering engines are so complex they cannot reasonably be secured, so need to be sandboxed for protection.

Unfortunately, I suspect that security experts within Apple were well aware of this, but were overruled because iOS devices tend to not have much RAM, and the user experience would be severely degraded by doing proper process-per-origin isolation, due to RAM exhaustion.