The bug

The command stat AffectedEntities is always set to 1 when a command without a player index is executed.

How to reproduce

1. :

   /scoreboard objectives add stats dummy
   

2. :

   scoreboard players set affectedEntities stats 0
   

3. :

   /scoreboard objectives setdisplay sidebar stats
   

4. Run in command block:

   /setblock ~ ~1 ~ command_block default replace {Command:"/say Test",CommandStats:{AffectedEntitiesName:"affectedEntities",AffectedEntitiesObjective:"stats"}}
   

5. Activate the new command block
   → The score of "affectedEntities" is now 1

The reason

The following is based on a decompiled version of Minecraft 1.10 using MCP 9.30.

The reason for this is that the method net.minecraft.command.CommandHandler.executeCommand(ICommandSender, String) sets the affected entities stat to 1 if the command contains no player index.