Notification API Leaks Private Repository Issue Titles After Collaborator Permission Revocation

@@ -8,8 +8,8 @@ import (
 	"net/url"
 
 	activities_model "code.gitea.io/gitea/models/activities"
-	"code.gitea.io/gitea/models/perm"
 	access_model "code.gitea.io/gitea/models/perm/access"
+	"code.gitea.io/gitea/modules/log"
 	api "code.gitea.io/gitea/modules/structs"
 )
 
@@ -25,11 +25,17 @@ func ToNotificationThread(ctx context.Context, n *activities_model.Notification)
 
 	// since user only get notifications when he has access to use minimal access mode
 	if n.Repository != nil {
-		result.Repository = ToRepo(ctx, n.Repository, access_model.Permission{AccessMode: perm.AccessModeRead})
-
-		// This permission is not correct and we should not be reporting it
-		for repository := result.Repository; repository != nil; repository = repository.Parent {
-			repository.Permissions = nil
+		perm, err := access_model.GetUserRepoPermission(ctx, n.Repository, n.User)
+		if err != nil {
+			log.Error("GetUserRepoPermission failed: %v", err)
+			return result
+		}
+		if perm.HasAnyUnitAccessOrPublicAccess() { // if user has been revoked access to repo, do not show repo info
+			result.Repository = ToRepo(ctx, n.Repository, perm)
+			// This permission is not correct and we should not be reporting it
+			for repository := result.Repository; repository != nil; repository = repository.Parent {
+				repository.Permissions = nil
+			}
 		}
 	}
 

@@ -0,0 +1,57 @@
+// Copyright 2026 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package convert
+
+import (
+	"testing"
+
+	activities_model "code.gitea.io/gitea/models/activities"
+	repo_model "code.gitea.io/gitea/models/repo"
+	"code.gitea.io/gitea/models/unittest"
+	user_model "code.gitea.io/gitea/models/user"
+	"code.gitea.io/gitea/modules/timeutil"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestToNotificationThreadIncludesRepoForAccessibleUser(t *testing.T) {
+	assert.NoError(t, unittest.PrepareTestDatabase())
+
+	n := newRepoNotification(t, 1, 4)
+	thread := ToNotificationThread(t.Context(), n)
+
+	if assert.NotNil(t, thread.Repository) {
+		assert.Equal(t, n.Repository.FullName(), thread.Repository.FullName)
+		assert.Nil(t, thread.Repository.Permissions)
+	}
+}
+
+func TestToNotificationThreadOmitsRepoWhenAccessRevoked(t *testing.T) {
+	assert.NoError(t, unittest.PrepareTestDatabase())
+
+	n := newRepoNotification(t, 2, 4)
+	thread := ToNotificationThread(t.Context(), n)
+
+	assert.Nil(t, thread.Repository)
+}
+
+func newRepoNotification(t *testing.T, repoID, userID int64) *activities_model.Notification {
+	t.Helper()
+
+	ctx := t.Context()
+	repo := unittest.AssertExistsAndLoadBean(t, &repo_model.Repository{ID: repoID})
+	assert.NoError(t, repo.LoadOwner(ctx))
+	user := unittest.AssertExistsAndLoadBean(t, &user_model.User{ID: userID})
+
+	return &activities_model.Notification{
+		ID:          repoID*1000 + userID,
+		UserID:      user.ID,
+		RepoID:      repo.ID,
+		Status:      activities_model.NotificationStatusUnread,
+		Source:      activities_model.NotificationSourceRepository,
+		UpdatedUnix: timeutil.TimeStampNow(),
+		Repository:  repo,
+		User:        user,
+	}
+}