CVE-2026-4021: contest-gallery contest gallery – upload & vote photos, media, sell with paypal & stripe Improper Authentication

Vulnerability summary

CVE-2026-4021 is a high (CVSS 8.1) Improper Authentication vulnerability in contest-gallery contest gallery – upload & vote photos, media, sell with paypal & stripe. EPSS estimates a 0.76% chance of exploitation in the next 30 days, higher than 54.7% of scored vulnerabilities. Fixed in 28.1.6.

Timeline

1. 23-03-2026
   PublishedVulnerability first disclosed.
2. 08-04-2026
   Last modifiedVulnerability information updated.

Description

The Contest Gallery plugin for WordPress is vulnerable to an authentication bypass leading to admin account takeover in all versions up to, and including, 28.1.5. This is due to the email confirmation handler in `users-registry-check-after-email-or-pin-confirmation.php` using the user's email string in a `WHERE ID = %s` clause instead of the numeric user ID, combined with an unauthenticated key-based login endpoint in `ajax-functions-frontend.php`. When the non-default `RegMailOptional=1` setting is enabled, an attacker can register with a crafted email starting with the target user ID (e.g., `1poc@example.test`), trigger the confirmation flow to overwrite the admin's `user_activation_key` via MySQL integer coercion, and then use the `post_cg1l_login_user_by_key` AJAX action to authenticate as the admin without any credentials. This makes it possible for unauthenticated attackers to take over any WordPress administrator account and gain full site control.

• CWE-287Improper AuthenticationWhen an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct.