@@ -22,26 +22,53 @@ export function isSsrRequestHandler(
   return typeof value === 'function' && '__ng_request_handler__' in value;
 }
 
+/**
+ * A mapping of the characters which have to be escaped to be interpolated into HTML,
+ * to their entity equivalents.
+ */
+const HTML_ESCAPE_CHARACTER_MAP: Record<string, string> = {
+  '&': '&amp;',
+  '<': '&lt;',
+  '>': '&gt;',
+  '"': '&quot;',
+  "'": '&#39;',
+};
+
+/**
+ * Escapes the characters of a value which is interpolated into HTML text or into a quoted
+ * attribute value.
+ *
+ * @param text - The value to escape.
+ * @returns The escaped value.
+ */
+function escapeHtml(text: string): string {
+  return text.replace(/[&<>"']/g, (character) => HTML_ESCAPE_CHARACTER_MAP[character]);
+}
+
 /**
  * Generates a static HTML page with a meta refresh tag to redirect the user to a specified URL.
  *
  * This function creates a simple HTML page that performs a redirect using a meta tag.
  * It includes a fallback link in case the meta-refresh doesn't work.
  *
+ * The provided URL is HTML-escaped before being interpolated.
+ *
  * @param url - The URL to which the page should redirect.
  * @returns The HTML content of the static redirect page.
  */
 export function generateRedirectStaticPage(url: string): string {
+  const escapedUrl = escapeHtml(url);
+
   return `
 <!DOCTYPE html>
 <html>
   <head>
     <meta charset="utf-8">
     <title>Redirecting</title>
-    <meta http-equiv="refresh" content="0; url=${url}">
+    <meta http-equiv="refresh" content="0; url=${escapedUrl}">
   </head>
   <body>
-    <pre>Redirecting to <a href="${url}">${url}</a></pre>
+    <pre>Redirecting to <a href="${escapedUrl}">${escapedUrl}</a></pre>
   </body>
 </html>
 `.trim();
 
@@ -0,0 +1,34 @@
+/**
+ * @license
+ * Copyright Google LLC All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.dev/license
+ */
+
+import { generateRedirectStaticPage } from './utils';
+
+describe('generateRedirectStaticPage', () => {
+  it('escapes the ampersands of a redirect target', () => {
+    const page = generateRedirectStaticPage('https://example.com/docs?from=ssg&next=/ssg');
+
+    expect(page).toContain(
+      '<meta http-equiv="refresh" content="0; url=https://example.com/docs?from=ssg&amp;next=/ssg">',
+    );
+    expect(page).toContain(
+      '<a href="https://example.com/docs?from=ssg&amp;next=/ssg">' +
+        'https://example.com/docs?from=ssg&amp;next=/ssg</a>',
+    );
+  });
+
+  it('escapes characters which would break out of the attribute or the tag', () => {
+    const page = generateRedirectStaticPage(`/"><script>alert('1')</script>`);
+
+    expect(page).not.toContain('<script>');
+    expect(page).toContain(
+      '<meta http-equiv="refresh" content="0; url=' +
+        '/&quot;&gt;&lt;script&gt;alert(&#39;1&#39;)&lt;/script&gt;">',
+    );
+    expect(page).toContain('<a href="/&quot;&gt;&lt;script&gt;alert(&#39;1&#39;)&lt;/script&gt;">');
+  });
+});
@@ -30,8 +30,14 @@ import { Console } from '../console';
 import { AngularAppManifest, getAngularAppManifest } from '../manifest';
 import { AngularBootstrap, isNgModule } from '../utils/ng';
 import { promiseWithAbort } from '../utils/promise';
-import { VALID_REDIRECT_RESPONSE_CODES, isValidRedirectResponseCode } from '../utils/redirect';
-import { joinUrlParts, stripLeadingSlash } from '../utils/url';
+import {
+  NormalizedUrl,
+  VALID_REDIRECT_RESPONSE_CODES,
+  isValidRedirectResponseCode,
+  normalizeAndValidateRedirect,
+  normalizeAndValidateRoutePath,
+} from '../utils/redirect';
+import { addLeadingSlash, joinUrlParts, stripLeadingSlash } from '../utils/url';
 import {
   PrerenderFallback,
   RenderMode,
@@ -205,18 +211,23 @@ async function* handleRoute(options: {
       } else if (typeof redirectTo === 'string') {
         // Reference the route parameters by their position in the URL (see `buildPathWithParams`).
         const routeSegments = joinUrlParts(baseHref, currentRoutePath).split('/');
-        parentRoutes.set(metadata.route, {
-          ...metadata,
-          redirectTo: resolveRedirectTo(
-            parentRoute,
-            replaceRedirectParams(
-              route,
-              redirectTo,
-              (parameter) => `*${routeSegments.lastIndexOf(parameter)}`,
-            ),
+        const { url, error } = resolveRedirectTo(
+          parentRoute,
+          replaceRedirectParams(
+            route,
+            redirectTo,
+            (parameter) => `*${routeSegments.lastIndexOf(parameter)}`,
           ),
-          relativeRedirect: redirectTo[0] !== '/' ? true : undefined,
-        });
+        );
+        if (error !== undefined) {
+          yield { error: invalidRedirectError(metadata.route, error) };
+        } else {
+          parentRoutes.set(metadata.route, {
+            ...metadata,
+            redirectTo: url,
+            relativeRedirect: redirectTo[0] !== '/' ? true : undefined,
+          });
+        }
       } else {
         parentRoutes.set(metadata.route, metadata);
       }
@@ -470,14 +481,21 @@ async function* handleSSGRoute(
   if (redirectTo !== undefined) {
     // Reference the route parameters by their position in the URL (see `buildPathWithParams`).
     const routeSegments = joinUrlParts(baseHref, currentRoutePath).split('/');
-    meta.redirectTo = resolveRedirectTo(
+    const { url, error } = resolveRedirectTo(
       parentRoute,
       replaceRedirectParams(
         route,
         redirectTo,
         (parameter) => `*${routeSegments.lastIndexOf(parameter)}`,
       ),
     );
+    if (error !== undefined) {
+      yield { error: invalidRedirectError(currentRoutePath, error) };
+
+      return;
+    }
+
+    meta.redirectTo = url;
     meta.relativeRedirect = redirectTo[0] !== '/' ? true : undefined;
   }
 
@@ -530,20 +548,41 @@ async function* handleSSGRoute(
           .replace(URL_PARAMETER_GLOBAL_REGEXP, replacer)
           .replace(CATCH_ALL_REGEXP, replacer);
 
+        // A parameter value is only meaningful in the context of the route it is substituted into,
+        // so the composed path is what gets normalized and validated. This also catches values that
+        // only become unsafe once combined with the route, such as a protocol-relative `//`.
+        const { url: normalizedRoute, error: routeError } = normalizeAndValidateRoutePath(
+          addLeadingSlash(routeWithResolvedParams),
+        );
+        if (routeError !== undefined) {
+          yield {
+            error:
+              `The '${stripLeadingSlash(currentRoutePath)}' route produced an invalid ` +
+              `prerender path: ${routeError}`,
+          };
+
+          continue;
+        }
+
+        let resolvedRedirectTo: string | undefined;
+        if (redirectTo !== undefined) {
+          const { url, error } = resolveRedirectTo(
+            parentRoute.replace(URL_PARAMETER_GLOBAL_REGEXP, replacer),
+            replaceRedirectParams(route, redirectTo, (parameter) => params[parameter.slice(1)]),
+          );
+          if (error !== undefined) {
+            yield { error: invalidRedirectError(routeWithResolvedParams, error) };
+
+            continue;
+          }
+
+          resolvedRedirectTo = url;
+        }
+
         yield {
           ...meta,
-          route: routeWithResolvedParams,
-          redirectTo:
-            redirectTo === undefined
-              ? undefined
-              : resolveRedirectTo(
-                  parentRoute.replace(URL_PARAMETER_GLOBAL_REGEXP, replacer),
-                  replaceRedirectParams(
-                    route,
-                    redirectTo,
-                    (parameter) => params[parameter.slice(1)],
-                  ),
-                ),
+          route: normalizedRoute,
+          redirectTo: resolvedRedirectTo,
         };
       }
     } catch (error) {
@@ -590,7 +629,10 @@ function handlePrerenderParamsReplacement(
       );
     }
 
-    return parameterName === '**' ? `/${value}` : value;
+    // The matched placeholder includes the separator, so it has to be re-added. The documented
+    // value of a `**` parameter is a path, which may already carry it: re-adding it unconditionally
+    // would compose a root catch-all into a protocol-relative `//foo/bar`.
+    return parameterName === '**' ? addLeadingSlash(value) : value;
   };
 }
 
@@ -602,20 +644,36 @@ function handlePrerenderParamsReplacement(
  * it is returned as is. If it is a relative path, it is resolved based on the parent route path,
  * and, like in the Angular router, its query and fragment are ignored.
  *
+ * The resolved target is then normalized and validated, so that every `redirectTo` reaching the
+ * route tree is a safe HTTP(S) URL or same-origin path.
+ *
  * @param parentRoute - The path of the parent route.
  * @param redirectTo - The target path for redirection.
- * @returns The resolved redirect path as a string.
+ * @returns The normalized redirect target, or the reason it was rejected.
  */
-function resolveRedirectTo(parentRoute: string, redirectTo: string): string {
+function resolveRedirectTo(parentRoute: string, redirectTo: string): NormalizedUrl {
   if (redirectTo[0] === '/') {
-    // If the redirectTo path is absolute, return it as is.
-    return redirectTo;
+    // If the redirectTo path is absolute, use it as is.
+    return normalizeAndValidateRedirect(redirectTo);
   }
 
   // Match Angular router behavior: replace all segments matched by the route.
   const [path] = redirectTo.split(/[?#]/, 1);
 
-  return joinUrlParts(parentRoute.replace(URL_PARAMETER_GLOBAL_REGEXP, '*'), path);
+  return normalizeAndValidateRedirect(
+    joinUrlParts(parentRoute.replace(URL_PARAMETER_GLOBAL_REGEXP, '*'), path),
+  );
+}
+
+/**
+ * Builds the diagnostic emitted when a route's `redirectTo` cannot be normalized.
+ *
+ * @param routePath - The route the `redirectTo` is defined on.
+ * @param reason - The reason reported by the redirect normalization.
+ * @returns The error message to report.
+ */
+function invalidRedirectError(routePath: string, reason: string): string {
+  return `The 'redirectTo' value for the '${stripLeadingSlash(routePath)}' route is invalid: ${reason}`;
 }
 
 /**
@@ -706,6 +764,27 @@ function buildServerConfigRouteTree({ routes, appShellRoute }: ServerRoutesConfi
   return { serverConfigRouteTree, errors };
 }
 
+/**
+ * Builds the key used to de-duplicate an extracted route.
+ *
+ * `RouteTree` percent-decodes every segment when a route is inserted, so two route paths which
+ * differ only in their encoding land on the same node, where the later one overwrites the earlier.
+ * De-duplication therefore runs on the decoded path rather than on the path as it was written:
+ * a prerendered path is normalized by the URL parser while the path of every other render mode is
+ * not, so the same route can be reached in both an encoded and an unencoded form.
+ *
+ * @param route - The route path to build a key for.
+ * @returns The decoded route path.
+ */
+function routeDeduplicationKey(route: string): string {
+  try {
+    return route.split('/').map(decodeURIComponent).join('/');
+  } catch {
+    // A malformed percent escape is reported when the route is inserted into the route tree.
+    return route;
+  }
+}
+
 /**
  * Retrieves routes from the given Angular application.
  *
@@ -829,7 +908,7 @@ export async function getRoutesFromAngularRouterConfig(
 
         // If a result already exists for the exact same route, subsequent matches should be ignored.
         // This aligns with Angular's app router behavior, which prioritizes the first route.
-        const routePath = routeMetadata.route;
+        const routePath = routeDeduplicationKey(routeMetadata.route);
         if (!seenRoutes.has(routePath)) {
           routesResults.push(routeMetadata);
           seenRoutes.add(routePath);