CVE-2026-19804 s2Member <= 260814 - Unauthenticated Remote Code Execution via 'first_name' Parameter in PayPal Proxy Return
Unauthenticated attackers can execute arbitrary code on WordPress sites using the s2Member plugin if a specific tracking template is configured and the proxy key is exposed.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-19804?
CVE-2026-19804 is a high-severity code injection vulnerability in clavaque s2Member – Excellent for All Kinds of Memberships, Content Restriction Paywalls & Member Access Subscriptions, published on 25 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
The s2Member – Excellent for All Kinds of Memberships, Content Restriction Paywalls & Member Access Subscriptions plugin for WordPress is vulnerable to Remote Code Execution in all versions up to, and including, 260814 via the 'first_name' parameter parameter. This is due to insufficient sanitization of the first_name parameter via esc_refs(), which strips only regex backreferences and not PHP tags, before substitution into the eval'd Signup Tracking Codes template, combined with disclosure of the site-global proxy verification key that allows PayPal postback verification to be bypassed. This makes it possible for unauthenticated attackers to execute code on the server. Successful exploitation requires that the site administrator has configured a Signup Tracking Codes template containing the %%first_name%% placeholder (a documented, GUI-supported feature) and that the attacker has obtained the site-global proxy verification key, which is exposed in plaintext in the JSON response of any PayPal Checkout AJAX request on the target site.
Weakness: CWE-94
Which versions are affected by CVE-2026-19804?
How do I fix CVE-2026-19804?
No fix has been published for CVE-2026-19804 yet. Limit exposure of the affected software until one is available.
Upgrade, and never evaluate templates, expressions or code built from user input. More about Code injection.
Is CVE-2026-19804 being exploited?
There is no known exploitation of CVE-2026-19804 in the wild and no public exploit code.
Sources
Also known as GHSA-fgx2-6hhq-hwhw.