User Registration & Membership <= 5.1.4 - Unauthenticated Open Redirect via 'redirect_to_on_logout' Parameter
Strategic Overview
- Status
- Patched in 5.1.5
- Affected Version
<= 5.1.4- CVSS
- 6.1Medium
- Weakness type
- CWE-601 · URL Redirection to Untrusted Site ('Open Redirect')
- CVE
CVE-2026-6203
At a glance
CVE-2026-6203 is a medium-severity URL Redirection to Untrusted Site ('Open Redirect') vulnerability in the User Registration & Membership WordPress plugin, affecting versions <= 5.1.4. It carries a CVSS score of 6.1 (reachable over the network; low attack complexity). Exploitation requires no authentication. The issue is fixed in version 5.1.5; sites on affected versions should update now. Disclosed April 2026, reported by Louis Deschanel (JeanJeanLeHaxor).
Vulnerability Overview
The User Registration & Membership plugin for WordPress is vulnerable to Open Redirect in versions up to and including 5.1.4. This is due to insufficient validation of user-supplied URLs passed via the 'redirect_to_on_logout' GET parameter before redirecting users. The `redirect_to_on_logout` GET parameter is passed directly to WordPress's `wp_redirect()` function instead of the domain-restricted `wp_safe_redirect()`. While `esc_url_raw()` is applied to sanitize malformed URLs, it does not restrict the redirect destination to the local domain, allowing an attacker to craft a specially formed link that redirects users to potentially malicious external URLs after logout, which could be used to facilitate phishing attacks.
Technical Analysis
The vector marks this flaw as remotely reachable over the network, with low attack complexity — no special timing or configuration is needed, and no privileges on the target site.
CWE-601: URL Redirection to Untrusted Site ('Open Redirect')
User Registration & Membership <= 5.1.4 carries this weakness at redirect_to_on_logout, and reaching it takes no account at all. An open redirect is a page that takes a destination from the request and sends the browser there without checking that the destination belongs to the site.
A link that starts on a trusted domain finishes on an attacker's, which is what makes phishing and consent-screen abuse credible to the person clicking it. For User Registration & Membership the fix is 5.1.5: builds <= 5.1.4 are affected, anything from 5.1.5 onward is not.
Remediation
Update to version 5.1.5, or a newer patched version
How does WordSec protect against this?
Requests carrying this pattern arrive without a session, so nothing upstream of the firewall gets a chance to reject them: WordSec's web application firewall inspects request payloads before WordPress loads them. None of that substitutes for the fix: User Registration & Membership 5.1.5 closes this, and updating the plugin is the step that ends it.
- Firewall
- Login Security
- Alerts
External References
Related records
Other vulnerabilities in User Registration & Membership – Free & Paid Memberships, Subscriptions, Content Restriction, User Profile, Custom User Registration & Login Builder
- 9.9CVE-2023-3342: User Registration <= 3.0.2 Arbitrary File Upload
CVE-2023-3342 - 9.8CVE-2026-32488: User Registration & Membership RCE
CVE-2026-32488 - 9.8CVE-2026-1492: User Registration & Membership Privilege Escalation
CVE-2026-1492 - 9.8CVE-2025-2563: User Registration & Membership Privilege Escalation
CVE-2025-2563 - 8.8CVE-2024-2417: User Registration Authenticated (Subscriber+)
CVE-2024-2417 - 8.8CVE-2023-3343: User Registration <= 3.0.1 PHP Object Injection
CVE-2023-3343 - 8.8CVE-2022-3912: User Registration <= 2.2.4 Arbitrary File Upload
CVE-2022-3912 - 8.1CVE-2026-11961: User Registration & Membership Privilege Escalation
CVE-2026-11961
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