diff --git a/content/browser/webui/web_ui_url_loader_factory.cc b/content/browser/webui/web_ui_url_loader_factory.cc
index 8bd18013afd9f..ebc314dc3d8ee 100644
--- a/content/browser/webui/web_ui_url_loader_factory.cc
+++ b/content/browser/webui/web_ui_url_loader_factory.cc
@@ -288,6 +288,18 @@ class WebUIURLLoaderFactory : public network::SelfDeletingURLLoaderFactory {
            allowed_hosts_.find(request.url.GetHost()) != allowed_hosts_.end()))
         << "Incorrect host: " << request.url.GetHost();
 
+    // SECURITY: the blob-internals / network-error / dino special cases below
+    // bypass URLDataManagerBackend host validation entirely. They must only be
+    // reachable for the chrome:// scheme; this factory is also instantiated for
+    // chrome-search:// (handed to the third-party remote-NTP renderer with an
+    // empty allowed_hosts set) and chrome-untrusted://, and those renderers
+    // must not be able to read profile-wide blob-internals.
+    if (scheme_ != kChromeUIScheme) {
+      CHECK_NE(request.url.host(), kChromeUIBlobInternalsHost);
+      CHECK_NE(request.url.host(), kChromeUINetworkErrorHost);
+      CHECK_NE(request.url.host(), kChromeUIDinoHost);
+    }
+
     if (request.url.host() == kChromeUIBlobInternalsHost) {
       GetIOThreadTaskRunner({})->PostTask(
           FROM_HERE,