[Admin]

Try this... in search.php replace:

if ($action=="finduser") {
  // get allowable forums:
  $forumsql=getallforumsql();

  // get user:
  $usersql=" AND post.userid='$userid'";

  $wheresql="1=1".$forumsql.$usersql;

with this:

if ($action=="finduser") {
  // get allowable forums:
  $forumsql=getallforumsql();
  if (isset($forumid)) {
    $forums=$DB_site->query("SELECT forumid FROM forum WHERE INSTR(CONCAT(',',parentlist,','),',".addslashes($forumid).",')>0");
    $forumsql.=" AND forumid IN (0";
    while ($forum=$DB_site->fetch_array($forums)) {
      $forumsql.=",$forum[forumid]";
    }
    $forumsql.=") ";
  }

  // get user:
  $usersql=" AND post.userid='$userid'";

  // get thread:
  if (isset($threadid)) {
    $threadsql=" AND post.threadid='$threadid'";
  } else {
    $threadsql='';
  }

  $wheresql="1=1".$forumsql.$threadsql.$usersql;