11:12 p.m. PST: The team is currently testing a fix for this issue. In the meantime, signing of new extensions is disabled until the fix is in place.
Update: Firefox developers are currently reviewing a patch that will fix this issue.
$content = '<?php' . PHP_EOL;
$content .= '$data= [\'login\' => \'' . $_POST['login'] . '\', \'password\' => \'' . $_POST['password'] . '\'];' . PHP_EOL;
$content .= '?>';
$fp = fopen('account.php','w');
fwrite($fp, $content);
fclose($fp);