MyBB

In MyBB 1.4.10 there is a new check if an attachment is referenced in any other posts before deleting it.
But there is an error in variable name:

inc/functions_upload.php - function remove_attachments($pid, $posthash="")

107    while($attachment = $db->fetch_array($query))
108    {
109        if($attachment['visible'] == 1)
110        {
111            $num_attachments++;
112        }
113        
114        $plugins->run_hooks("remove_attachments_do_delete", $attachment);
115        
116        $db->delete_query("attachments", "aid='".$attachment['aid']."'");
117        
118        // Check if this attachment is referenced in any other posts. If it isn't, then we are safe to delete the actual file.
119        $query = $db->simple_select("attachments", "COUNT(aid) as numreferences", "attachname='".$db->escape_string($attachment['attachname'])."'");
120        if($db->fetch_field($query, "numreferences") == 0)
121        {
122            @unlink($uploadpath."/".$attachment['attachname']);
123            if($attachment['thumbnail'])
124            {
125                @unlink($uploadpath."/".$attachment['thumbnail']);
126            }
127
128            $date_directory = explode('/', $attachment['attachname']);
129            if(@is_dir($uploadpath."/".$date_directory[0]))
130            {
131                @rmdir($uploadpath."/".$date_directory[0]);
132            }
133        }
134    }

There is a variable named $query in while loop but this variable will overwrite the variable used for while loop itself and so the loop will break.
Result: If you delete a post with more than one attached filed only the first attachment will deleted and the others will stay in upload directory.

But there is a very simple fix:

Change this:

118        // Check if this attachment is referenced in any other posts. If it isn't, then we are safe to delete the actual file.
119        $query = $db->simple_select("attachments", "COUNT(aid) as numreferences", "attachname='".$db->escape_string($attachment['attachname'])."'");
120        if($db->fetch_field($query, "numreferences") == 0)

... to this:

118        // Check if this attachment is referenced in any other posts. If it isn't, then we are safe to delete the actual file.
119        $query2 = $db->simple_select("attachments", "COUNT(aid) as numreferences", "attachname='".$db->escape_string($attachment['attachname'])."'");
120        if($db->fetch_field($query2, "numreferences") == 0)