CVE-2026-104803
CriticalCVSS 9.8Summary
The WPCOM Member plugin for WordPress (versions up to and including 1.7.27) contains an authentication bypass in its social-login callback handler. Missing nonce validation, OAuth state verification, and per-visitor session namespace isolation allow an unauthenticated attacker to inject a forged session entry and log in as any WordPress user, including administrators, if their bound openid/unionid is known.
Risk Assessment
An attacker can gain full control of a WordPress administrator account, leading to complete site compromise. Exploitation requires at least one configured social provider and knowledge of the victim's bound identifier.
Recommendation
Update the WPCOM Member plugin to a version later than 1.7.27 or disable it if no update is available. Consider restricting access to social-login endpoints.
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Original NVD description (English source)
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.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS