The MC4WP: Mailchimp for WordPress plugin for WordPress is vulnerable to Missing Authorization in all versions up to, and including, 4.11.1. This is due to the plugin trusting the `_mc4wp_action` POST parameter without validation, allowing unauthenticated attackers to force the form to process unsubscribe actions instead of subscribe actions. This makes it possible for unauthenticated attackers to arbitrarily unsubscribe any email address from the connected Mailchimp audience via the `_mc4wp_action` parameter, granted they can obtain the form ID (which is publicly exposed in the HTML source).
Attack Parameters
Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Privileges Required
None
No privileges needed
User Interaction
None
No user interaction needed
Impact Assessment
Confidentiality
None
No data leak
Integrity
Low
Partial data modification
Availability
Low
Partial disruption
CVSS Vector v3.1
Weakness Type (CWE)
References 7
https://cwe.mitre.org/data/definitions/862.html
security@wordfence.com
https://github.com/ibericode/mailchimp-for-wordpress/commit/5fdebc2a5e22d11287d…
security@wordfence.com
https://plugins.trac.wordpress.org/browser/mailchimp-for-wp/tags/4.11.1/include…
security@wordfence.com
https://plugins.trac.wordpress.org/browser/mailchimp-for-wp/tags/4.11.1/include…
security@wordfence.com
https://plugins.trac.wordpress.org/browser/mailchimp-for-wp/tags/4.11.1/include…
security@wordfence.com
https://plugins.trac.wordpress.org/changeset?sfp_email=&sfph_mail=&reponame=&ne…
security@wordfence.com
https://www.wordfence.com/threat-intel/vulnerabilities/id/10262aa9-5656-4a2b-ae…
security@wordfence.com