From 5e6beb57c2777190688cd5b369c3337af4951327 Mon Sep 17 00:00:00 2001
From: levlam <levlam@telegram.org>
Date: Fri, 10 Jul 2026 20:54:01 +0300
Subject: Accept messageActionChangeCommunity only with accessible communities.

---
 td/telegram/CommunityManager.cpp |  5 +++++
 td/telegram/CommunityManager.h   |  2 ++
 td/telegram/UpdatesManager.cpp   | 14 +++++++++++++-
 td/telegram/UpdatesManager.h     |  3 +++
 4 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/td/telegram/CommunityManager.cpp b/td/telegram/CommunityManager.cpp
index 734ce999d..deda69dc5 100644
--- a/td/telegram/CommunityManager.cpp
+++ b/td/telegram/CommunityManager.cpp
@@ -346,6 +346,11 @@ bool CommunityManager::have_community(CommunityId community_id) const {
   return communities_.count(community_id) > 0;
 }
 
+bool CommunityManager::have_accessible_community(CommunityId community_id) const {
+  const auto *c = get_community(community_id);
+  return c != nullptr && c->access_hash != 0;
+}
+
 const CommunityManager::Community *CommunityManager::get_community(CommunityId community_id) const {
   return communities_.get_pointer(community_id);
 }
diff --git a/td/telegram/CommunityManager.h b/td/telegram/CommunityManager.h
index c2d3a621b..92ae2718a 100644
--- a/td/telegram/CommunityManager.h
+++ b/td/telegram/CommunityManager.h
@@ -37,6 +37,8 @@ class CommunityManager final : public Actor {
 
   bool have_community_force(CommunityId community_id, const char *source);
 
+  bool have_accessible_community(CommunityId community_id) const;
+
   void reload_community(CommunityId community_id, Promise<Unit> &&promise, const char *source);
 
   void on_get_community(telegram_api::community &community, const char *source);
diff --git a/td/telegram/UpdatesManager.cpp b/td/telegram/UpdatesManager.cpp
index 09562db8c..fe7769342 100644
--- a/td/telegram/UpdatesManager.cpp
+++ b/td/telegram/UpdatesManager.cpp
@@ -20,6 +20,7 @@
 #include "td/telegram/ChannelType.h"
 #include "td/telegram/ChatId.h"
 #include "td/telegram/ChatManager.h"
+#include "td/telegram/CommunityManager.h"
 #include "td/telegram/ConfigManager.h"
 #include "td/telegram/DialogAction.h"
 #include "td/telegram/DialogActionManager.h"
@@ -722,6 +723,11 @@ bool UpdatesManager::is_acceptable_channel(ChannelId channel_id) const {
   return td_->chat_manager_->have_channel_force(channel_id, "is_acceptable_channel");
 }
 
+bool UpdatesManager::is_acceptable_community(CommunityId community_id) const {
+  return td_->community_manager_->have_community_force(community_id, "is_acceptable_community") &&
+         td_->community_manager_->have_accessible_community(community_id);
+}
+
 bool UpdatesManager::is_acceptable_peer(const tl_object_ptr<telegram_api::Peer> &peer) const {
   if (peer == nullptr) {
     return true;
@@ -992,7 +998,6 @@ bool UpdatesManager::is_acceptable_message(const telegram_api::Message *message_
         case telegram_api::messageActionPollAppendAnswer::ID:
         case telegram_api::messageActionPollDeleteAnswer::ID:
         case telegram_api::messageActionManagedBotCreated::ID:
-        case telegram_api::messageActionChangeCommunity::ID:
           break;
         case telegram_api::messageActionChatCreate::ID: {
           auto action = static_cast<const telegram_api::messageActionChatCreate *>(action_ptr);
@@ -1110,6 +1115,13 @@ bool UpdatesManager::is_acceptable_message(const telegram_api::Message *message_
           }
           break;
         }
+        case telegram_api::messageActionChangeCommunity::ID: {
+          auto action = static_cast<const telegram_api::messageActionChangeCommunity *>(action_ptr);
+          if (action->community_id_ != 0 && !is_acceptable_community(CommunityId(action->community_id_))) {
+            return false;
+          }
+          break;
+        }
         default:
           UNREACHABLE();
           return false;
diff --git a/td/telegram/UpdatesManager.h b/td/telegram/UpdatesManager.h
index 6bb30d48d..9a47a007c 100644
--- a/td/telegram/UpdatesManager.h
+++ b/td/telegram/UpdatesManager.h
@@ -8,6 +8,7 @@
 
 #include "td/telegram/ChannelId.h"
 #include "td/telegram/ChatId.h"
+#include "td/telegram/CommunityId.h"
 #include "td/telegram/DialogId.h"
 #include "td/telegram/InputGroupCallId.h"
 #include "td/telegram/MessageFullId.h"
@@ -491,6 +492,8 @@ class UpdatesManager final : public Actor {
 
   bool is_acceptable_channel(ChannelId channel_id) const;
 
+  bool is_acceptable_community(CommunityId community_id) const;
+
   bool is_acceptable_peer(const tl_object_ptr<telegram_api::Peer> &peer) const;
 
   bool is_acceptable_message_entities(const vector<tl_object_ptr<telegram_api::MessageEntity>> &message_entities) const;
-- 
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