MyBB Community Forums

At the top of moderation.php:

$tid = intval($mybb->input['tid']);
$pid = intval($mybb->input['pid']);
$fid = intval($mybb->input['fid']);

if($pid)
{
	$post = get_post($pid);
	$tid = $post['tid'];
	if(!$post['pid'])
	{
		error($lang->error_invalidpost);
	}
}

Now, search for:

case "do_multideleteposts":

Scroll down and you'll find this:

		if($pids)
		{
			$query = $db->simple_select("threads", "tid", "firstpost IN({$pids})");
			while($tid = $db->fetch_field($query, "tid"))
			{
				$tids[] = $tid;
			}
		}

Here:

while($tid = $db->fetch_field($query, "tid"))

$tid will override the existing $tid and depending on the circunstances, it might be null / 0 / whatever you want to call it.

Now, scroll down a little bit more and you'll find:

			$query = $db->simple_select("posts", "*", "tid='$tid'");
			$numposts = $db->num_rows($query);
			if(!$numposts)
			{
				$moderation->delete_thread($tid);
				mark_reports($tid, "thread");
				$url = get_forum_link($fid);
			}
			else
			{
				mark_reports($plist, "posts");
				$url = get_thread_link($thread['tid']);
			}

Obviously, this will not work:

$query = $db->simple_select("posts", "*", "tid='$tid'");

So this is what's executed always:

			if(!$numposts)
			{
				$moderation->delete_thread($tid);
				mark_reports($tid, "thread");
				$url = get_forum_link($fid);
			}

(or at least most of the times, like I said, it depends if one of posts we're trying to delete is the first post or not but if it's not, it will still run that code)

By simply changing this:

			while($tid = $db->fetch_field($query, "tid"))
			{
				$tids[] = $tid;
			}

to:

			while($threadid = $db->fetch_field($query, "tid"))
			{
				$tids[] = $threadid;
			}

The bug is fixed. I've searched the duplicate, fixed and the forum I am posting it and couldn't find this report so I decided to post this.

Does all of that code happen under the case "do_multideleteposts"?

Yes, except the first bit of code I posted

Corresponding Ticket: http://dev.mybboard.net/issues/401