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CVE-2026-104803

CRITICAL 9.8 CVSS 3.1
Published
October 10, 2026
Last modified
October 13, 2026
NVD status
Deferred
Reported by
security@wordfence.com
Weakness
CWE-287
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Description

The WPCOM Member plugin for WordPress is vulnerable to Authentication Bypass in all versions up to, and including, 1.7.27 via the `uuid` and `code` parameters of the social-login callback handler registered on the `init` hook. The vulnerability exists because the `login` function's social-login flow performs no nonce validation, no OAuth state verification, and no per-visitor namespace isolation in the session store, allowing an unauthenticated attacker to issue a crafted GET request that writes an attacker-named, attacker-valued entry into the global session namespace (bypassing the per-visitor prefix by prepending an underscore), then issue a second GET request triggering `weapp_new_user()` to read that forged entry and resolve the attacker-supplied `openid` value to a bound WordPress account before `wp_set_auth_cookie()` establishes a fully authenticated session. This makes it possible for unauthenticated attackers to log in as any WordPress user — including administrators — whose bound social provider identifier (openid/unionid) is known or discoverable. Successful exploitation requires that the target site has at least one social provider configured (which activates the vulnerable handler) and that the attacker knows or can enumerate the victim account's bound openid or unionid.

Affected WordPress components

A confirmed match is backed by the plugin or theme slug. A possible match is based on the product name only and should be verified.

Affected products and versions

  • whyun WPCOM Member — Up to and including 1.7.27

References