diff --git a/ios/chrome/credential_provider_extension/ui/credential_list_mediator_unittest.mm b/ios/chrome/credential_provider_extension/ui/credential_list_mediator_unittest.mm
index c4f5206af6969..e7da2ba74da38 100644
--- a/ios/chrome/credential_provider_extension/ui/credential_list_mediator_unittest.mm
+++ b/ios/chrome/credential_provider_extension/ui/credential_list_mediator_unittest.mm
@@ -526,4 +526,89 @@ TEST_F(CredentialListMediatorTest, FilterPasswordCredentialsNoFalseMatch) {
   ASSERT_EQ(filteredCredentials.count, 0u);
 }
 
+// Tests that a credential saved for an apex domain is NOT suggested when the
+// requesting host lives under a private registry (Public Suffix List entry)
+// that happens to be a subdomain of that apex. Because the CPE never
+// PSL-normalizes the requesting host before the hasSuffix: comparison, this
+// test currently FAILS, demonstrating the asymmetric-match vulnerability.
+//
+// Concrete example: "up.railway.app" is on the PSL (private section), so
+// eTLD+1("attacker.up.railway.app", INCLUDE_PRIVATE) == "attacker.up.railway.app",
+// which is a different registrable domain from "railway.app". The CPE must not
+// place the railway.app credential in the Suggested list for that host.
+TEST_F(CredentialListMediatorTest,
+       FilterPasswordCredentialsNoPSLPrivateRegistryFalseMatch) {
+  // Credential as it would be archived by Chrome after the victim saves a
+  // password at https://railway.app/: registryControlledDomain is computed in
+  // the browser via net::registry_controlled_domains::GetDomainAndRegistry(
+  //     url, INCLUDE_PRIVATE_REGISTRIES) == "railway.app".
+  ArchivableCredential* apexCredential =
+      [[ArchivableCredential alloc] initWithFavicon:nil
+                                               gaia:nil
+                                           password:@"victim-apex-password"
+                                               rank:1
+                                   recordIdentifier:@"recordIdentifier"
+                                  serviceIdentifier:@"https://railway.app/"
+                                        serviceName:@"railway.app"
+                           registryControlledDomain:@"railway.app"
+                                           username:@"victim@example.com"
+                                               note:@""
+                                       lastUsedTime:0];
+
+  id<CredentialStore> credentialStore = [[MockCredentialStore alloc]
+      initWithCredentials:@[ apexCredential ]];
+
+  // iOS supplies the full page URL for web logins
+  // (ASCredentialServiceIdentifierTypeURL); HostForServiceIdentifier()
+  // extracts the bare NSURL.host without any PSL lookup.
+  ASCredentialServiceIdentifier* attackerTenant =
+      [[ASCredentialServiceIdentifier alloc]
+          initWithIdentifier:@"https://attacker.up.railway.app/login"
+                        type:ASCredentialServiceIdentifierTypeURL];
+
+  CredentialListMediator* mediator = [[CredentialListMediator alloc]
+               initWithConsumer:nil
+                      UIHandler:nil
+                credentialStore:credentialStore
+             serviceIdentifiers:@[ attackerTenant ]
+      credentialResponseHandler:nil];
+
+  mediator.allCredentials = [mediator fetchAllCredentials];
+  NSArray<id<Credential>>* filtered = [mediator filterCredentials];
+
+  // EXPECTED (correct PSL-aware behaviour): 0 — different registrable domain.
+  // ACTUAL (current code): 1 — the apex credential is incorrectly Suggested
+  // because [@"attacker.up.railway.app" hasSuffix:@".railway.app"] == YES.
+  EXPECT_EQ(filtered.count, 0u)
+      << "railway.app credential must NOT be Suggested for "
+         "attacker.up.railway.app (separate registrable domain per PSL)";
+
+  // Also exercise the fallback branch (registryControlledDomain empty), which
+  // has the same asymmetry against credential.serviceIdentifier's bare host.
+  ArchivableCredential* apexCredentialNoRCD =
+      [[ArchivableCredential alloc] initWithFavicon:nil
+                                               gaia:nil
+                                           password:@"victim-apex-password"
+                                               rank:1
+                                   recordIdentifier:@"recordIdentifier2"
+                                  serviceIdentifier:@"https://railway.app/"
+                                        serviceName:@"railway.app"
+                           registryControlledDomain:@""
+                                           username:@"victim@example.com"
+                                               note:@""
+                                       lastUsedTime:0];
+  id<CredentialStore> credentialStore2 = [[MockCredentialStore alloc]
+      initWithCredentials:@[ apexCredentialNoRCD ]];
+  CredentialListMediator* mediator2 = [[CredentialListMediator alloc]
+               initWithConsumer:nil
+                      UIHandler:nil
+                credentialStore:credentialStore2
+             serviceIdentifiers:@[ attackerTenant ]
+      credentialResponseHandler:nil];
+  mediator2.allCredentials = [mediator2 fetchAllCredentials];
+  NSArray<id<Credential>>* filtered2 = [mediator2 filterCredentials];
+  EXPECT_EQ(filtered2.count, 0u)
+      << "fallback branch (bare-host serviceIdentifier) is also vulnerable";
+}
+
 }  // namespace credential_provider_extension