diff --git a/index.bs b/index.bs
index f0ea8fb..5c07165 100644
--- a/index.bs
+++ b/index.bs
@@ -140,6 +140,12 @@ WebView APIs let the host app inject and execute JavaScript and CSS into an site
 
 ### Sandbox / process isolation ### {#sandbox-process-isolation}
 
+ > [[threat-model-web#sandboxed-web-content-execution-and-rendering|Implementations may also use origin- or site-based isolation strategies so that unrelated web content cannot interfere during normal use or following a compromise, but the exact isolation unit is browser-specific.]]
+
+WebViews inherit the sandbox of their engine, but the isolation unit is effectively chosen by the [=host app=]:
+it decides how many WebView instances share a process, and the native bridge gives content running in the sandboxed process a path into app-privileged code.
+Neither the user nor the loaded site can tell which isolation guarantees apply.
+
 Issue(#2): How does sandboxing and process isolation work in WebViews?
 
 ### Transport: TLS, mixed content ### {#transport}