fix(http): prevent caching of responses with Set-Cookie headers

Skip HttpTransferCache serialization for HTTP responses that contain a
Set-Cookie header.

Cookie-setting responses commonly represent session-specific,
user-specific, or security-sensitive state. Serializing their bodies into
SSR TransferState can embed sensitive data into the generated HTML, where
it may be reused during hydration or replayed by a shared cache/CDN.

(cherry picked from commit 80795defc6)

adev/src/content/guide/ssr.md

@@ -432,7 +432,7 @@ To configure this, update your `angular.json` file as follows:
 You can customize how Angular caches HTTP responses during server‑side rendering (SSR) and reuses them during hydration by configuring `HttpTransferCacheOptions`.  
 This configuration is provided globally using `withHttpTransferCacheOptions` inside `provideClientHydration()`.
 
-By default, `HttpClient` caches all `HEAD` and `GET` requests which don't contain `Authorization`, `Proxy-Authorization`, or `Cookie` headers and are not sent with `withCredentials` or Fetch API `credentials` modes that can send credentials. Angular also skips transfer cache when a request or response includes `Cache-Control` directives that forbid caching (`no-store`, `no-cache`, or `private`), or when the Fetch API `cache` option is set to `no-store` or `no-cache`. You can override the request filtering settings by using `withHttpTransferCacheOptions` in the hydration configuration.
+By default, `HttpClient` caches all `HEAD` and `GET` requests which don't contain `Authorization`, `Proxy-Authorization`, or `Cookie` headers and are not sent with `withCredentials` or Fetch API `credentials` modes that can send credentials. Angular also skips transfer cache when a request or response includes `Cache-Control` directives that forbid caching (`no-store`, `no-cache`, or `private`), or when the Fetch API `cache` option is set to `no-store` or `no-cache`. Responses that carry a `Set-Cookie` header are also skipped. You can override the request filtering settings by using `withHttpTransferCacheOptions` in the hydration configuration.
 
 ```ts
 import {bootstrapApplication} from '@angular/platform-browser';
@@ -560,7 +560,7 @@ To disable caching for an individual request, you can specify the [`transferCach
 httpClient.get('/api/sensitive-data', {transferCache: false});
 ```
 
-`HttpTransferCache` does not cache requests or responses that explicitly opt out of caching. Angular skips transfer cache entries when a request includes a `Cache-Control` header with `no-store`, `no-cache`, or `private`, or when the request uses the Fetch API `cache` option set to `no-store` or `no-cache`. Responses with `Cache-Control: no-store`, `Cache-Control: no-cache`, or `Cache-Control: private` are also not stored in the transfer cache.
+`HttpTransferCache` does not cache requests or responses that explicitly opt out of caching. Angular skips transfer cache entries when a request includes a `Cache-Control` header with `no-store`, `no-cache`, or `private`, or when the request uses the Fetch API `cache` option set to `no-store` or `no-cache`. Responses with `Cache-Control: no-store`, `Cache-Control: no-cache`, or `Cache-Control: private` are also not stored in the transfer cache. Responses that include a `Set-Cookie` header are likewise not stored, as they typically carry user-specific state.
 
 NOTE: If your application uses different HTTP origins to make API calls on the server and on the client, the `HTTP_TRANSFER_CACHE_ORIGIN_MAP` token allows you to establish a mapping between those origins, so that `HttpTransferCache` feature can recognize those requests as the same ones and reuse the data cached on the server during hydration on the client.
 

packages/common/http/src/transfer_cache.ts

@@ -288,8 +288,10 @@ export function transferCacheInterceptorFn(
           const {headers, body, status, statusText} = event;
 
           // Only cache successful HTTP responses that do not have Cache-Control
-          // directives that forbid shared caching (no-store or private).
-          if (hasUncacheableCacheControl(headers)) {
+          // directives that forbid shared caching (no-store or private) and do not
+          // carry a Set-Cookie header. A Set-Cookie header marks the response as
+          // user-specific.
+          if (hasUncacheableCacheControl(headers) || hasSetCookieHeader(headers)) {
             return;
           }
 
@@ -344,6 +346,10 @@ function hasUncacheableCacheControl(headers: HttpHeaders): boolean {
   });
 }
 
+function hasSetCookieHeader(headers: HttpHeaders): boolean {
+  return headers.has('set-cookie');
+}
+
 function isNonCacheableRequest(cache: RequestCache): boolean {
   return cache === 'no-cache' || cache === 'no-store';
 }

packages/common/http/test/transfer_cache_spec.ts

@@ -215,6 +215,32 @@ describe('TransferCache', () => {
       expect(secondNext).toHaveBeenCalledTimes(1);
     });
 
+    it('should not cache responses with a Set-Cookie header', () => {
+      configureInterceptor();
+
+      const request = new HttpRequest('GET', '/test-set-cookie');
+
+      const firstNext = jasmine.createSpy('firstNext').and.returnValue(
+        of(
+          new HttpResponse({
+            body: 'user-a-session',
+            headers: new HttpHeaders({'Set-Cookie': 'session=user-a; HttpOnly'}),
+          }),
+        ),
+      );
+      const secondNext = jasmine
+        .createSpy('secondNext')
+        .and.returnValue(of(new HttpResponse({body: 'user-b-session'})));
+
+      runOnServer(() => {
+        expect(runInterceptor(request, firstNext).body).toBe('user-a-session');
+        expect(runInterceptor(request, secondNext).body).toBe('user-b-session');
+      });
+
+      expect(firstNext).toHaveBeenCalledTimes(1);
+      expect(secondNext).toHaveBeenCalledTimes(1);
+    });
+
     it('should not cache requests with Cache-Control: no-store', () => {
       configureInterceptor();
 
@@ -591,6 +617,14 @@ describe('TransferCache', () => {
       makeRequestAndExpectOne('/test-private', 'fresh-data');
     });
 
+    it('should not cache responses with a Set-Cookie header', () => {
+      makeRequestAndExpectOne('/test-set-cookie', 'user-a-session', {
+        responseHeaders: {'Set-Cookie': 'session=user-a; HttpOnly'},
+      });
+
+      makeRequestAndExpectOne('/test-set-cookie', 'user-b-session');
+    });
+
     it('should not cache responses with Cache-Control containing no-store among other directives', () => {
       makeRequestAndExpectOne('/test-multi', 'data', {
         responseHeaders: {'Cache-Control': 'max-age=0, no-store, must-revalidate'},