WordPress/wp-admin/plugin-editor.php

<?php
require_once('admin.php');

$title = __("Edit Plugins");
$parent_file = 'plugins.php';

wp_reset_vars(array('action', 'redirect', 'profile', 'error', 'warning', 'a', 'file'));

$plugins = get_plugins();
$plugin_files = array_keys($plugins);

if (empty($file)) {
	$file = $plugin_files[0];
}

$file = validate_file_to_edit($file, $plugin_files);
$real_file = get_real_file_to_edit( PLUGINDIR . "/$file");

switch($action) {

case 'update':

	check_admin_referer('edit-plugin_' . $file);

	if ( !current_user_can('edit_plugins') )
		wp_die('<p>'.__('You do not have sufficient permissions to edit templates for this blog.').'</p>');

	$newcontent = stripslashes($_POST['newcontent']);
	if (is_writeable($real_file)) {
		$f = fopen($real_file, 'w+');
		fwrite($f, $newcontent);
		fclose($f);
		wp_redirect("plugin-editor.php?file=$file&a=te");
	} else {
		wp_redirect("plugin-editor.php?file=$file");
	}

	exit();

break;

default:

	if ( !current_user_can('edit_plugins') )
		wp_die('<p>'.__('You do not have sufficient permissions to edit plugins for this blog.').'</p>');

	require_once('admin-header.php');

	update_recently_edited(PLUGINDIR . "/$file");

	if (!is_file($real_file))
		$error = 1;

	if (!$error) {
		$f = fopen($real_file, 'r');
		$content = fread($f, filesize($real_file));
		$content = htmlspecialchars($content);
	}

	?>
<?php if (isset($_GET['a'])) : ?>
 <div id="message" class="updated fade"><p><?php _e('File edited successfully.') ?></p></div>
<?php endif; ?>
 <div class="wrap"> 
  <?php
	if (is_writeable($real_file)) {
		echo '<h2>' . sprintf(__('Editing <strong>%s</strong>'), $file) . '</h2>';
	} else {
		echo '<h2>' . sprintf(__('Browsing <strong>%s</strong>'), $file) . '</h2>';
	}
	?>
	<div id="templateside">
<h3><?php _e('Plugin files') ?></h3>

<?php
if ($plugin_files) :
?>
  <ul>
<?php foreach($plugin_files as $plugin_file) : ?>
		 <li><a href="plugin-editor.php?file=<?php echo "$plugin_file"; ?>"><?php echo $plugins[$plugin_file]['Name']; ?></a></li>
<?php endforeach; ?>
  </ul>
<?php endif; ?>
</div>
	<?php	if (!$error) { ?> 
  <form name="template" id="template" action="plugin-editor.php" method="post">
  <?php wp_nonce_field('edit-plugin_' . $file) ?>
		 <div><textarea cols="70" rows="25" name="newcontent" id="newcontent" tabindex="1"><?php echo $content ?></textarea> 
     <input type="hidden" name="action" value="update" /> 
     <input type="hidden" name="file" value="<?php echo $file ?>" /> 
		</div>
<?php if ( is_writeable($real_file) ) : ?>
     <p class="submit">
<?php
	echo "<input type='submit' name='submit' value='	" . __('Update File &raquo;') . "' tabindex='2' />";
?>
</p>
<?php else : ?>
<p><em><?php _e('If this file were writable you could edit it.'); ?></em></p>
<?php endif; ?>
   </form> 
  <?php
	} else {
		echo '<div class="error"><p>' . __('Oops, no such file exists! Double check the name and try again, merci.') . '</p></div>';
	}
	?>
<div class="clear"> &nbsp; </div>
</div> 
<?php
break;
}

include("admin-footer.php") ?>