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Move has cross-site ancestor to the environment, from the ESO #11540

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Move has cross-site ancestor to the environment, from the ESO #11540

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a0cdf7c
Move `has cross-site ancestor` to the environment, from the ESO
bvandersloot-mozilla Aug 1, 2025
dcb9bd4
fixing bug in review and nits
bvandersloot-mozilla Sep 15, 2025
57be3c4
Use the request's currentURL's origin
bvandersloot-mozilla Sep 16, 2025
ed33f02
fix trailing whitespace
bvandersloot-mozilla Sep 25, 2025
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Original file line number Diff line number Diff line change
Expand Up @@ -92621,8 +92621,8 @@ interface <dfn interface>BarProp</dfn> {
<p>To <dfn>set up a window environment settings object</dfn>, given a <span>URL</span>
<var>creationURL</var>, a <span>JavaScript execution context</span> <var>execution context</var>,
null or an <span>environment</span> <var>reservedEnvironment</var>, a <span>URL</span>
<var>topLevelCreationURL</var>, and an <span>origin</span> <var>topLevelOrigin</var>, run these
steps:</p>
<var>topLevelCreationURL</var>, an <span>origin</span> <var>topLevelOrigin</var>, and a
boolean <var>hasCrossSiteAncestor</var>:</p>

<ol>
<li><p>Let <var>realm</var> be the value of <var>execution context</var>'s Realm
Expand Down Expand Up @@ -92660,30 +92660,6 @@ interface <dfn interface>BarProp</dfn> {
<span data-x="concept-document-window">associated <code>Document</code></span>.</p>
</dd>

<dt>The <span data-x="concept-settings-object-has-cross-site-ancestor">has cross-site
ancestor</span></dt>
<dd>
<ol>
<li><p>If <var>window</var>'s <span>navigable</span>'s <span
data-x="nav-parent">parent</span> is null, then return false.</p></li>

<li><p>Let <var>parentDocument</var> be <var>window</var>'s <span>navigable</span>'s <span
data-x="nav-parent">parent</span>'s <span data-x="nav-document">active
document</span>.</p></li>

<li><p>If <var>parentDocument</var>'s <span>relevant settings object</span>'s <span
data-x="concept-settings-object-has-cross-site-ancestor">has cross-site ancestor</span> is
true, then return true.</p></li>

<li><p>If <var>parentDocument</var>'s <span data-x="concept-document-origin">origin</span>
is not <span>same site</span> with <var>window</var>'s <span
data-x="concept-document-window">associated <code>Document</code></span>'s <span
data-x="concept-document-origin">origin</span>, then return true.</p></li>

<li><p>Return false.</p></li>
</ol>
</dd>

<dt>The <span data-x="concept-settings-object-policy-container">policy container</span></dt>
<dd>
<p>Return the <span data-x="concept-document-policy-container">policy container</span> of
Expand Down Expand Up @@ -92748,8 +92724,10 @@ interface <dfn interface>BarProp</dfn> {

<li><p>Set <var>settings object</var>'s <span data-x="concept-environment-creation-url">creation
URL</span> to <var>creationURL</var>, <var>settings object</var>'s <span>top-level creation
URL</span> to <var>topLevelCreationURL</var>, and <var>settings object</var>'s <span>top-level
origin</span> to <var>topLevelOrigin</var>.</p></li>
URL</span> to <var>topLevelCreationURL</var>, <var>settings object</var>'s <span>top-level
origin</span> to <var>topLevelOrigin</var>, and <var>settings object</var>'s <span
data-x="concept-environment-cross-site-ancestor">has cross-site ancestor</span> to
<var>hasCrossSiteAncestor</var>.</p></li>

<li><p>Set <var>realm</var>'s [[HostDefined]] field to <var>settings object</var>.</p></li>
</ol>
Expand Down Expand Up @@ -100111,9 +100089,20 @@ interface <dfn interface>NotRestoredReasons</dfn> {
otherwise <var>embedder</var>'s <span>relevant settings object</span>'s <span>top-level
origin</span>.</p></li>

<li><p>Let <var>hasCrossSiteAncestor</var> be false.</p></li>

<li><p>If <var>embedder</var> is not null, then set <var>hasCrossSiteAncestor</var> to
<var>embedder</var>'s <span>relevant settings object</span>'s <span
data-x="concept-environment-cross-site-ancestor"> has cross-site ancestor</span>.</p></li>

<li><p>If <var>embedder</var> is not null, and <var>origin</var> is not <span>same site</span>
with <var>embedder</var>'s <span>relevant settings object</span>'s <span
data-x="concept-settings-object-origin">origin</span>, then set <var>hasCrossSiteAncestor</var>
to true.</p></li>

<li><p><span>Set up a window environment settings object</span> with <code>about:blank</code>,
<var>realm execution context</var>, null, <var>topLevelCreationURL</var>, and
<var>topLevelOrigin</var>.</p></li>
<var>realm execution context</var>, null, <var>topLevelCreationURL</var>,
<var>topLevelOrigin</var>, and <var>hasCrossSiteAncestor</var>.</p></li>

<li><p>Let <var>loadTimingInfo</var> be a new <span>document load timing info</span> with
its <span>navigation start time</span> set to the result of calling <span>coarsen time</span>
Expand Down Expand Up @@ -104209,6 +104198,8 @@ location.href = '#foo';</code></pre>

<li><p>Let <var>topLevelOrigin</var> be null.</p></li>

<li><p>Let <var>hasCrossSiteAncestor</var> be false.</p></li>

<li>
<p>If <var>navigable</var> is not a <span>top-level traversable</span>, then:</p>

Expand All @@ -104222,6 +104213,15 @@ location.href = '#foo';</code></pre>

<li><p>Set <var>topLevelOrigin</var> to <var>parentEnvironment</var>'s <span>top-level
origin</span>.</p></li>

<li><p>Set <var>hasCrossSiteAncestor</var> to <var>parentEnvironment</var>'s <span
data-x="concept-environment-cross-site-ancestor">has cross-site ancestor</span>.</p></li>

<li><p>If <var>parentEnvironment</var>'s <span
data-x="concept-settings-object-origin">origin</span> is not <span>same site</span> with
<var>navigable</var>'s <span data-x="nav-document">active document</span>'s <span>relevant
settings object</span>'s <span data-x="concept-settings-object-origin">origin</span>, then
set <var>hasCrossSiteAncestor</var> to true.</p></li>
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Unless I'm misunderstanding the goal here, "navigable's active documents' relevant settings object" seems like the wrong thing to inspect here.

(Side note: as a nit, if you have a document, you can just check its concept-document-origin directly instead of getting its relevant settings object.)

Consider navigating an iframe from embedded in https://a.example/ from https://a.example/ to https://b.example/ which redirects to https://c.example/. What the spec as written in this PR does:

  • parentEnvironment's origin is https://a.example.
  • navigable's active document's (relevant settings object's) origin is also https://a.example, since the document currently active in the iframe is displaying https://a.example/
  • So, we set hasCrossSiteAncestor to false.
  • So, the reserved client we create sets it to false.
  • The same is true for both legs of the redirect, i.e. both paths through the step 21 "While true" loop.

I think you probably want to use responseOrigin, which is computed down in step 21.11. It's... not obvious how to pull step 21.11 up to before 21.2, since it depends on step 21.10, which depends on step 21.9, which depends on step 21.2.

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Yikes, that is subtle and doesn't have an obvious answer. The best I can come up with is updating the reservedClient upon receiving the responseOrigin in 21.11.

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I'll add it and flag it in the changes here, though it feels a little hacky.

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I discussed this with @bvandersloot-mozilla and suggested using request's current URL's origin. We can't wait for a response to determine an origin, for the same reason as with top-level partitioning, we need to have the partition before we do the request.

This does raise the question as to whether a request partition and response partition should be different and I'm not sure we have good test coverage for that. I think they should probably be the same. (Sandboxing can make a difference here.)

Another question it raised to me is what happens when a service worker returns a CORS response from another origin. That either has to network error or we have to use the request's current URL's origin. (A service worker should not be able to create a document that's cross-origin from itself.) I thought this was accounted for in Fetch or HTML, but I can't find it.

</ol>
</li>

Expand All @@ -104232,8 +104232,10 @@ location.href = '#foo';</code></pre>
data-x="concept-environment-target-browsing-context">target browsing context</span> is
<var>navigable</var>'s <span data-x="nav-bc">active browsing context</span>, <span
data-x="concept-environment-creation-url">creation URL</span> is <var>currentURL</var>,
<span>top-level creation URL</span> is <var>topLevelCreationURL</var>, and <span>top-level
origin</span> is <var>topLevelOrigin</var>.</p>
<span>top-level creation URL</span> is <var>topLevelCreationURL</var>, <span>top-level
origin</span> is <var>topLevelOrigin</var>, and <span
data-x="concept-environment-cross-site-ancestor">has cross-site ancestor</span> is
<var>hasCrossSiteAncestor</var>.</p>

<p class="note">The created environment's <span
data-x="concept-environment-active-service-worker">active service worker</span> is set in
Expand Down Expand Up @@ -106737,6 +106739,8 @@ location.href = '#foo';</code></pre>
<li><p>Let <var>topLevelOrigin</var> be <var>navigationParams</var>'s <span
data-x="navigation-params-origin">origin</span>.</p></li>

<li><p>Let <var>hasCrossSiteAncestor</var> be false.</p></li>

<li>
<p>If <var>navigable</var>'s <span data-x="nav-container">container</span> is not null,
then:</p>
Expand All @@ -106750,13 +106754,22 @@ location.href = '#foo';</code></pre>

<li><p>Set <var>topLevelOrigin</var> to <var>parentEnvironment</var>'s <span>top-level
origin</span>.</p></li>

<li><p>Set <var>hasCrossSiteAncestor</var> to <var>parentEnvironment</var>'s <span
data-x="concept-environment-cross-site-ancestor">has cross-site ancestor</span>.</p></li>

<li><p>If <var>navigationParams</var>'s <span
data-x="navigation-params-request">origin</span> is not <span>same site</span> with
<var>parentEnvironment</var>'s <span data-x="concept-settings-object-origin">origin</span>,
then set <var>hasCrossSiteAncestor</var> to true.</p>
</ol>
</li>

<li><p><span>Set up a window environment settings object</span> with <var>creationURL</var>,
<var>realmExecutionContext</var>, <var>navigationParams</var>'s <span
data-x="navigation-params-reserved-environment">reserved environment</span>,
<var>topLevelCreationURL</var>, and <var>topLevelOrigin</var>.</p></li>
<var>topLevelCreationURL</var>, <var>topLevelOrigin</var>, and
<var>hasCrossSiteAncestor</var>.</p></li>
</ol>

<p class="note">This is the usual case, where the new <code>Document</code> we're about to
Expand Down Expand Up @@ -108624,6 +108637,15 @@ new PaymentRequest(&hellip;); // Allowed to use
involved.</p>
</dd>

<dt>A <dfn data-x="concept-environment-cross-site-ancestor" export for="environment">has
cross-site ancestor</dfn></dt>
<dd><p>A boolean. For window <span>environment settings object</span>s this will be set to true
if an ancestor frame has an <span data-x="concept-settings-object-origin">origin</span> that is
not <span>same site</span> with the current window's <span
data-x="concept-settings-object-origin">origin</span> and otherwise false. For workers and
worklets it is set to the <span data-x="concept-environment-cross-site-ancestor">has cross-site
ancestor</span> of its creator.</p></dd>

<dt>A <dfn data-x="concept-environment-target-browsing-context" export
for="environment">target browsing context</dfn></dt>
<dd><p>Null or a target <span>browsing context</span> for a <span
Expand Down Expand Up @@ -108687,10 +108709,6 @@ new PaymentRequest(&hellip;); // Allowed to use
<p>An <span>origin</span> used in security checks.</p>
</dd>

<dt>A <dfn data-x="concept-settings-object-has-cross-site-ancestor" export
for="environment settings object">has cross-site ancestor</dfn></dt>
<dd><p>A boolean used in security checks.</p></dd>

<dt>A <dfn data-x="concept-settings-object-policy-container" export
for="environment settings object">policy container</dfn></dt>

Expand Down Expand Up @@ -123514,23 +123532,6 @@ interface <dfn interface>SharedWorkerGlobalScope</dfn> : <span>WorkerGlobalScope
origin</var> otherwise.</p>
</dd>

<dt>The <span data-x="concept-settings-object-has-cross-site-ancestor">has cross-site
ancestry</span></dt>
<dd>
<ol>
<li><p>If <var>outside settings</var>'s <span
data-x="concept-settings-object-has-cross-site-ancestor">has cross-site ancestor</span> is
true, then return true.</p></li>

<li><p>If <var>worker global scope</var>'s <span
data-x="concept-WorkerGlobalScope-url">url</span>'s <span
data-x="concept-url-scheme">scheme</span> is "<code data-x="">data</code>", then return
true.</p></li>

<li><p>Return false.</p></li>
</ol>
</dd>

<dt>The <span data-x="concept-settings-object-policy-container">policy container</span></dt>
<dd>
<p>Return <var>worker global scope</var>'s <span
Expand All @@ -123555,8 +123556,10 @@ interface <dfn interface>SharedWorkerGlobalScope</dfn> : <span>WorkerGlobalScope
unique opaque string, <span data-x="concept-environment-creation-url">creation URL</span> to
<var>worker global scope</var>'s <span>url</span>, <span>top-level creation URL</span> to null,
<span data-x="concept-environment-target-browsing-context">target browsing context</span> to
null, and <span data-x="concept-environment-active-service-worker">active service worker</span>
to null.</p></li>
null, <span data-x="concept-environment-active-service-worker">active service worker</span>
to null, and <span data-x="concept-environment-cross-site-ancestor">has cross-site
ancestor</span> to <var>outside settings</var>'s <span
data-x="concept-environment-cross-site-ancestor">has cross-site ancestor</span>.</p></li>

<li><p>If <var>worker global scope</var> is a <code>DedicatedWorkerGlobalScope</code> object,
then set <var>settings object</var>'s <span>top-level origin</span> to <var>outside
Expand Down Expand Up @@ -124813,10 +124816,6 @@ interface <dfn interface>WorkletGlobalScope</dfn> {};</code></pre>
<p>Return <var>origin</var>.</p>
</dd>

<dt>The <span data-x="concept-settings-object-has-cross-site-ancestor">has cross-site
ancestor</span></dt>
<dd><p>Return true.</p></dd>

<dt>The <span data-x="concept-settings-object-policy-container">policy container</span></dt>
<dd>
<p>Return <var>inheritedPolicyContainer</var>.</p>
Expand Down