Only use supported sort order for "explore/users" page (#29430)

Thanks to inferenceus : some sort orders on the "explore/users" page
could list users by their lastlogintime/updatetime.

It leaks user's activity unintentionally. This PR makes that page only
use "supported" sort orders.

Removing the "sort orders" could also be a good solution, while IMO at
the moment keeping the "create time" and "name" orders is also fine, in
case some users would like to find a target user in the search result,
the "sort order" might help.

![image](https://github.com/go-gitea/gitea/assets/2114189/ce5c39c1-1e86-484a-80c3-33cac6419af8)

5 files changed, 79 insertions, 6 deletions

diff --git a/models/user/search.go b/models/user/search.go
index 0fa278c257..9484bf4425 100644
--- a/models/user/search.go
+++ b/models/user/search.go
@@ -9,6 +9,7 @@ import (
 	"strings"
 
 	"code.gitea.io/gitea/models/db"
+	"code.gitea.io/gitea/modules/container"
 	"code.gitea.io/gitea/modules/structs"
 	"code.gitea.io/gitea/modules/util"
 
@@ -30,6 +31,8 @@ type SearchUserOptions struct {
 	Actor         *User // The user doing the search
 	SearchByEmail bool  // Search by email as well as username/full name
 
+	SupportedSortOrders container.Set[string] // if not nil, only allow to use the sort orders in this set
+
 	IsActive           util.OptionalBool
 	IsAdmin            util.OptionalBool
 	IsRestricted       util.OptionalBool
diff --git a/routers/web/explore/org.go b/routers/web/explore/org.go
index 4a468482ae..f8fd6ec38e 100644
--- a/routers/web/explore/org.go
+++ b/routers/web/explore/org.go
@@ -6,6 +6,7 @@ package explore
 import (
 	"code.gitea.io/gitea/models/db"
 	user_model "code.gitea.io/gitea/models/user"
+	"code.gitea.io/gitea/modules/container"
 	"code.gitea.io/gitea/modules/setting"
 	"code.gitea.io/gitea/modules/structs"
 	"code.gitea.io/gitea/services/context"
@@ -24,8 +25,16 @@ func Organizations(ctx *context.Context) {
 		visibleTypes = append(visibleTypes, structs.VisibleTypeLimited, structs.VisibleTypePrivate)
 	}
 
-	if ctx.FormString("sort") == "" {
-		ctx.SetFormString("sort", setting.UI.ExploreDefaultSort)
+	supportedSortOrders := container.SetOf(
+		"newest",
+		"oldest",
+		"alphabetically",
+		"reversealphabetically",
+	)
+	sortOrder := ctx.FormString("sort")
+	if sortOrder == "" {
+		sortOrder = "newest"
+		ctx.SetFormString("sort", sortOrder)
 	}
 
 	RenderUserSearch(ctx, &user_model.SearchUserOptions{
@@ -33,5 +42,7 @@ func Organizations(ctx *context.Context) {
 		Type:        user_model.UserTypeOrganization,
 		ListOptions: db.ListOptions{PageSize: setting.UI.ExplorePagingNum},
 		Visible:     visibleTypes,
+
+		SupportedSortOrders: supportedSortOrders,
 	}, tplExploreUsers)
 }
diff --git a/routers/web/explore/user.go b/routers/web/explore/user.go
index b67fac2fc1..41f440f9d9 100644
--- a/routers/web/explore/user.go
+++ b/routers/web/explore/user.go
@@ -10,6 +10,7 @@ import (
 	"code.gitea.io/gitea/models/db"
 	user_model "code.gitea.io/gitea/models/user"
 	"code.gitea.io/gitea/modules/base"
+	"code.gitea.io/gitea/modules/container"
 	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/setting"
 	"code.gitea.io/gitea/modules/sitemap"
@@ -79,10 +80,16 @@ func RenderUserSearch(ctx *context.Context, opts *user_model.SearchUserOptions,
 		fallthrough
 	default:
 		// in case the sortType is not valid, we set it to recentupdate
+		sortOrder = "recentupdate"
 		ctx.Data["SortType"] = "recentupdate"
 		orderBy = "`user`.updated_unix DESC"
 	}
 
+	if opts.SupportedSortOrders != nil && !opts.SupportedSortOrders.Contains(sortOrder) {
+		ctx.NotFound("unsupported sort order", nil)
+		return
+	}
+
 	opts.Keyword = ctx.FormTrim("q")
 	opts.OrderBy = orderBy
 	if len(opts.Keyword) == 0 || isKeywordValid(opts.Keyword) {
@@ -132,8 +139,16 @@ func Users(ctx *context.Context) {
 	ctx.Data["PageIsExploreUsers"] = true
 	ctx.Data["IsRepoIndexerEnabled"] = setting.Indexer.RepoIndexerEnabled
 
-	if ctx.FormString("sort") == "" {
-		ctx.SetFormString("sort", setting.UI.ExploreDefaultSort)
+	supportedSortOrders := container.SetOf(
+		"newest",
+		"oldest",
+		"alphabetically",
+		"reversealphabetically",
+	)
+	sortOrder := ctx.FormString("sort")
+	if sortOrder == "" {
+		sortOrder = "newest"
+		ctx.SetFormString("sort", sortOrder)
 	}
 
 	RenderUserSearch(ctx, &user_model.SearchUserOptions{
@@ -142,5 +157,7 @@ func Users(ctx *context.Context) {
 		ListOptions: db.ListOptions{PageSize: setting.UI.ExplorePagingNum},
 		IsActive:    util.OptionalBoolTrue,
 		Visible:     []structs.VisibleType{structs.VisibleTypePublic, structs.VisibleTypeLimited, structs.VisibleTypePrivate},
+
+		SupportedSortOrders: supportedSortOrders,
 	}, tplExploreUsers)
 }
diff --git a/templates/explore/search.tmpl b/templates/explore/search.tmpl
index 74b80436dc..2bb5f319d1 100644
--- a/templates/explore/search.tmpl
+++ b/templates/explore/search.tmpl
@@ -16,8 +16,6 @@
 			<a class="{{if eq .SortType "oldest"}}active {{end}}item" href="{{$.Link}}?sort=oldest&q={{$.Keyword}}">{{ctx.Locale.Tr "repo.issues.filter_sort.oldest"}}</a>
 			<a class="{{if eq .SortType "alphabetically"}}active {{end}}item" href="{{$.Link}}?sort=alphabetically&q={{$.Keyword}}">{{ctx.Locale.Tr "repo.issues.label.filter_sort.alphabetically"}}</a>
 			<a class="{{if eq .SortType "reversealphabetically"}}active {{end}}item" href="{{$.Link}}?sort=reversealphabetically&q={{$.Keyword}}">{{ctx.Locale.Tr "repo.issues.label.filter_sort.reverse_alphabetically"}}</a>
-			<a class="{{if eq .SortType "recentupdate"}}active {{end}}item" href="{{$.Link}}?sort=recentupdate&q={{$.Keyword}}">{{ctx.Locale.Tr "repo.issues.filter_sort.recentupdate"}}</a>
-			<a class="{{if eq .SortType "leastupdate"}}active {{end}}item" href="{{$.Link}}?sort=leastupdate&q={{$.Keyword}}">{{ctx.Locale.Tr "repo.issues.filter_sort.leastupdate"}}</a>
 		</div>
 	</div>
 </div>
diff --git a/tests/integration/explore_user_test.go b/tests/integration/explore_user_test.go
new file mode 100644
index 0000000000..046caf378e
--- /dev/null
+++ b/tests/integration/explore_user_test.go
@@ -0,0 +1,44 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package integration
+
+import (
+	"net/http"
+	"testing"
+
+	"code.gitea.io/gitea/tests"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestExploreUser(t *testing.T) {
+	defer tests.PrepareTestEnv(t)()
+
+	cases := []struct{ sortOrder, expected string }{
+		{"", "/explore/users?sort=newest&q="},
+		{"newest", "/explore/users?sort=newest&q="},
+		{"oldest", "/explore/users?sort=oldest&q="},
+		{"alphabetically", "/explore/users?sort=alphabetically&q="},
+		{"reversealphabetically", "/explore/users?sort=reversealphabetically&q="},
+	}
+	for _, c := range cases {
+		req := NewRequest(t, "GET", "/explore/users?sort="+c.sortOrder)
+		resp := MakeRequest(t, req, http.StatusOK)
+		h := NewHTMLParser(t, resp.Body)
+		href, _ := h.Find(`.ui.dropdown .menu a.active.item[href^="/explore/users"]`).Attr("href")
+		assert.Equal(t, c.expected, href)
+	}
+
+	// these sort orders shouldn't be supported, to avoid leaking user activity
+	cases404 := []string{
+		"/explore/users?sort=lastlogin",
+		"/explore/users?sort=reverselastlogin",
+		"/explore/users?sort=leastupdate",
+		"/explore/users?sort=reverseleastupdate",
+	}
+	for _, c := range cases404 {
+		req := NewRequest(t, "GET", c).SetHeader("Accept", "text/html")
+		MakeRequest(t, req, http.StatusNotFound)
+	}
+}