whyun WPCOM Member Plugin up to 1.7.27 on WordPress Social Login Callback weapp_new_user uuid/code improper authentication

Summaryinfo

A vulnerability described as critical has been identified in whyun WPCOM Member Plugin up to 1.7.27. Affected is the function weapp_new_user of the component Social Login Callback Handler. Such manipulation of the argument uuid/code leads to improper authentication. This vulnerability is uniquely identified as CVE-2026-104803. The attack can be launched remotely. No exploit exists.

Detailsinfo

A vulnerability, which was classified as critical, has been found in whyun WPCOM Member Plugin up to 1.7.27. Affected by this issue is the function weapp_new_user of the component Social Login Callback Handler. The manipulation of the argument uuid/code with an unknown input leads to a improper authentication vulnerability. Using CWE to declare the problem leads to CWE-287. When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct. Impacted is confidentiality, integrity, and availability. CVE summarizes:

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.

The advisory is available at wordfence.com. This vulnerability is handled as CVE-2026-104803 since 10/02/2026. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. Technical details are known, but there is no available exploit. The structure of the vulnerability defines a possible price range of USD $0-$5k at the moment (estimation calculated on 10/10/2026).

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-96279). If you want to get best quality of vulnerability data, you may have to visit VulDB.

Productinfo

Type

• WordPress Plugin

Vendor

• whyun

Name

• WPCOM Member Plugin

Version

• 1.7.0
• 1.7.1
• 1.7.2
• 1.7.3
• 1.7.4
• 1.7.5
• 1.7.6
• 1.7.7
• 1.7.8
• 1.7.9
• 1.7.10
• 1.7.11
• 1.7.12
• 1.7.13
• 1.7.14
• 1.7.15
• 1.7.16
• 1.7.17
• 1.7.18
• 1.7.19
• 1.7.20
• 1.7.21
• 1.7.22
• 1.7.23
• 1.7.24
• 1.7.25
• 1.7.26
• 1.7.27

CPE 2.3info

• 🔒
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CPE 2.2info

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• 🔒

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Entryinfo

If you want to get best quality of vulnerability data, you may have to visit VulDB.

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