ProfilePress WordPress Plugin Membership Payment Bypass Vulnerability

The ProfilePress plugin for WordPress, specifically the “Paid Membership Plugin, Ecommerce, User Registration Form, Login Form, User Profile & Restrict Content” version 4.16.11 and earlier, contains a vulnerability (CVE-2026-3445) that allows authenticated attackers to bypass membership payment requirements. This flaw stems from a missing ownership verification on the change_plan_sub_id parameter within the process_checkout() function. An attacker with subscriber-level access can exploit this by referencing another user’s active subscription during the checkout process. This manipulation affects proration calculations, ultimately enabling the attacker to obtain paid lifetime membership plans without submitting legitimate payment. This vulnerability is triggered via the ppress_process_checkout AJAX action, making it critical for defenders to implement appropriate detection and mitigation strategies.

Attack Chain

1. An attacker registers a new account on the WordPress site with the vulnerable ProfilePress plugin installed, obtaining subscriber-level access.
2. The attacker identifies a valid, active subscription ID belonging to another user within the ProfilePress system.
3. The attacker initiates the purchase of a paid membership plan (e.g., a lifetime membership).
4. During the checkout process, the attacker intercepts the HTTP request sent to the ppress_process_checkout AJAX action.
5. The attacker modifies the change_plan_sub_id parameter within the request, replacing the expected value with the subscription ID of the other user.
6. The server-side process_checkout() function fails to properly validate the ownership of the provided change_plan_sub_id.
7. Due to the manipulated change_plan_sub_id, the proration calculations are skewed, resulting in a significantly reduced or zeroed payment amount.
8. The attacker completes the checkout process without making a legitimate payment and is granted access to the paid membership plan.

Impact

Successful exploitation of CVE-2026-3445 allows attackers to bypass payment requirements and gain unauthorized access to premium content and features offered through the ProfilePress plugin. This can result in significant revenue loss for website owners relying on paid memberships. The number of affected websites is potentially large, given the popularity of WordPress and the ProfilePress plugin. This vulnerability could also damage the reputation of the affected website and erode trust among legitimate paying members.

Recommendation

• Upgrade to ProfilePress version 4.16.12 or later to patch CVE-2026-3445 (reference: vulnerability description).
• Deploy the Sigma rule Detect ProfilePress Membership Bypass Attempt to your SIEM and tune for your environment to detect potential exploitation attempts by monitoring for the use of the ppress_process_checkout AJAX action with suspicious change_plan_sub_id values (reference: Sigma rule).
• Monitor web server logs for POST requests to the /wp-admin/admin-ajax.php endpoint with the action parameter set to ppress_process_checkout to identify potential exploit attempts (reference: Attack Chain).