pathname: terminate if cannot-be-a-base

components/script/dom/location.rs

@@ -197,7 +197,10 @@ impl LocationMethods for Location {
     // https://html.spec.whatwg.org/multipage/#dom-location-pathname
     fn SetPathname(&self, value: USVString) -> ErrorResult {
         self.check_same_origin_domain()?;
-        self.set_url_component(value, UrlHelper::SetPathname);
+        // If copyURL's cannot-be-a-base-URL flag is set, terminate these steps.
+        if !self.get_url().cannot_be_a_base() {
+            self.set_url_component(value, UrlHelper::SetPathname);
+        }
         Ok(())
     }