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CVE-2026-4021— Contest Gallery <= 28.1.5 - Unauthenticated Privilege Escalation Admin Account Takeover via Registration Confirmation Email-to-ID Type Confusion

Quick assessment

Affected
contest-gallery Contest Gallery – Upload & Vote Photos, Media, Sell with PayPal & Stripe
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

WordPress和WordPress plugin都是WordPress基金会的产品。WordPress是一套使用PHP语言开发的博客平台。该平台具有在基于PHP和MySQL的服务器上架设个人博客网站的功能。WordPress plugin是一个应用插件。 WordPress plugin Contest Gallery 28.1.5及之前版本存在授权问题漏洞，该漏洞源于身份验证绕过，可能导致管理员账户被接管。

CVSS 8.1 · High EPSS 0.73% · P53
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I. Basic Information for CVE-2026-4021

Vulnerability Information
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Vulnerability Title
Contest Gallery <= 28.1.5 - Unauthenticated Privilege Escalation Admin Account Takeover via Registration Confirmation Email-to-ID Type Confusion
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
认证机制不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
WordPress plugin Contest Gallery 授权问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
WordPress和WordPress plugin都是WordPress基金会的产品。WordPress是一套使用PHP语言开发的博客平台。该平台具有在基于PHP和MySQL的服务器上架设个人博客网站的功能。WordPress plugin是一个应用插件。 WordPress plugin Contest Gallery 28.1.5及之前版本存在授权问题漏洞，该漏洞源于身份验证绕过，可能导致管理员账户被接管。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
contest-gallery Contest Gallery – Upload & Vote Photos, Media, Sell with PayPal & Stripe * ~ 28.1.5 -

II. Public POCs for CVE-2026-4021

# POC Description Source Link Shenlong Link
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III. Intelligence Information for CVE-2026-4021

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Patches & Fixes for CVE-2026-4021 (5)

Vendor Advisories for CVE-2026-4021 (1)

IV. Related Vulnerabilities

Same product: Contest Gallery – Upload & Vote Photos, Media, Sell with PayPal & Stripe
Same vendor: contest-gallery
Same weakness: CWE-287

V. Comments for CVE-2026-4021

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