# s2Member <= 261106 - Unauthenticated Stored Cross-Site Scripting via PayPal Return Tracking Codes

- **ID:** WPSEC-2026-2903
- **Plugin:** s2Member – Excellent for All Kinds of Memberships, Content Restriction Paywalls & Member Access Subscriptions (`s2member`), https://wordpress.org/plugins/s2member/
- **Affected versions:** all versions before 261110
- **Fixed in:** 261110 (Update to 261110 or later.)
- **Severity:** Medium 4.7 (CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:L/A:N)
- **Weakness:** CWE-79
- **Usage among sites WPSec scans:** plugin Low, affected versions Low (as of 2026-11-12)
- **Attack surface analysis:** https://attacksurface.wpsec.com/plugin/s2member
- **Fix released:** 2026-11-10
- **Published:** 2026-11-12
- **URL:** https://wpsec.com/vuln/WPSEC-2026-2903/

## Description

The s2member plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the PayPal return-page tracking codes feature (Signup, Modification, Capability and Specific Post/Page tracking codes) in all versions up to, and including, 261106, due to insufficient sanitization of payer-supplied PayPal values (such as first name, last name, payer email, item name and custom values) inserted into the tracking code template, and the stored result being output through do_shortcode() without escaping. This makes it possible for unauthenticated attackers who complete a PayPal payment to inject arbitrary web scripts or shortcodes that run in the browser that processes the payment's return link, for example a user tricked into opening that link. Exploitation requires tracking codes with the affected placeholders to be configured.

## References

- https://wpsec.com/vuln/WPSEC-2026-2903/
- https://plugins.svn.wordpress.org/s2member/tags/261110/
- https://wordpress.org/plugins/s2member/

Source: WPSec, https://wpsec.com/vuln/WPSEC-2026-2903/

License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Free to use, share and adapt, also commercially, if you credit WPSec and link to this advisory.