Hello, your script contains an exploit, you can be exploited, do not run this script, you need to use the 'n' switch on $read(), and you need to use $unsafe() on %chan, you can read more about injection here https://en.wikichip.org/wiki/mirc/msl_injection

Also your script has missing { } on the if, here is a fixed version:

Code:
on *:connect:{
  if ($server == serveraddress) {
    var %x 1
    while ($read(autojoin.txt, nt ,%x) != $null) {
      var %chan $chr(35) $+ $v1
      .timerautojoin -m 1 $calc(%x * 333) JOIN $unsafe(%chan)
      inc %x
    }
  }
}

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