Improve receipt message validations.

app/src/main/java/org/thoughtcrime/securesms/database/GroupReceiptTable.kt

@@ -7,6 +7,7 @@ import androidx.core.content.contentValuesOf
 import org.signal.core.util.SqlUtil
 import org.signal.core.util.delete
 import org.signal.core.util.deleteAll
+import org.signal.core.util.exists
 import org.signal.core.util.forEach
 import org.signal.core.util.logging.Log
 import org.signal.core.util.readToList
@@ -127,6 +128,13 @@ class GroupReceiptTable(context: Context?, databaseHelper: SignalDatabase?) : Da
     }
   }
 
+  fun hasReceipt(mmsId: Long, recipientId: RecipientId): Boolean {
+    return readableDatabase
+      .exists(TABLE_NAME)
+      .where("$MMS_ID = ? AND $RECIPIENT_ID = ?", mmsId, recipientId)
+      .run()
+  }
+
   fun getGroupReceiptInfo(mmsId: Long): List<GroupReceiptInfo> {
     return readableDatabase
       .select()

app/src/main/java/org/thoughtcrime/securesms/database/MessageTable.kt

@@ -5540,6 +5540,11 @@ open class MessageTable(context: Context?, databaseHelper: SignalDatabase) : Dat
       return emptySet()
     }
 
+    // Only allow updating receipts for a group message if the sender is actually a member (stories are excluded because a single story timestamp can map to multiple messages)
+    if (!receiptData.forIndividualChat && receiptData.storyType == StoryType.NONE && !groupReceipts.hasReceipt(receiptData.messageId, receiptAuthor)) {
+      return emptySet()
+    }
+
     if (!receiptData.marked) {
       // We set the receipt_timestamp to the max of the two values because that single column represents the timestamp of the last receipt of any type.
       // That means we want to update it for each new receipt type, but we never want the time to go backwards.