Contact Zero

CVE-2026-104803

The WPCOM Member plugin for WordPress is vulnerable to Authentication Bypass in all versions up to, and including, 1.7.2

score 35CRITICAL 9.8

Summary

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.

Published 2026-10-10 · first seen here 2026-10-10

Analysis & write-ups

No technical write-up from a research team yet. Contact Zero checks Unit 42, Google/Mandiant, Microsoft, Talos, CrowdStrike, Rapid7, watchTowr and others several times a day, plus NVD and CISA reference links.

Where it shows in your logs

Server or web application · Authentication bypass or missing authorisation medium confidence

What to look for

Data sources

Web server and WAF logs · ATT&CK DS0015 Application Log Content

Sentinel
W3CIISLogAppServiceHTTPLogsAzureDiagnostics (Application Gateway / Front Door WAF)_Im_WebSession
Splunk
Web.Webms:iis:autoaccess_combinedWAF / proxy sourcetypes
CrowdStrike
Falcon Next-Gen SIEM: third-party web / WAF / proxy logs

Process creation · ATT&CK DS0009 Process Creation

Sentinel
DeviceProcessEventsSecurityEvent (4688)Sysmon Event ID 1_Im_ProcessCreate
Splunk
Endpoint.ProcessesXmlWinEventLog:Microsoft-Windows-Sysmon/OperationalWinEventLog:Security (4688)
CrowdStrike
ProcessRollup2SyntheticProcessRollup2

File creation · ATT&CK DS0022 File Creation

Sentinel
DeviceFileEventsSysmon Event ID 11_Im_FileEvent
Splunk
Endpoint.FilesystemSysmon Event ID 11
CrowdStrike
NewExecutableWrittenNewScriptWritten*FileWritten events

Network connections · ATT&CK DS0029 Network Connection Creation / Network Traffic Flow

Sentinel
DeviceNetworkEventsCommonSecurityLog (firewall)_Im_NetworkSession
Splunk
Network_Traffic.All_TrafficFirewall sourcetypes (pan:traffic, fortigate_traffic, cisco:asa)
CrowdStrike
NetworkConnectIP4NetworkReceiveAcceptIP4NetworkConnectIP6

Authentication and sessions · ATT&CK DS0028 Logon Session Creation / DS0002 User Account Authentication

Sentinel
SigninLogsSecurityEvent (4624, 4625, 4648)DeviceLogonEventsIdentityLogonEvents_Im_Authentication
Splunk
Authentication.Authenticationpan:globalprotectVPN sourcetypes
CrowdStrike
UserLogonUserLogonFailed2Falcon Identity Protection events

Account and group changes · ATT&CK DS0002 User Account Creation / Modification

Sentinel
SecurityEvent (4720, 4728, 4732, 4756)AuditLogsIdentityDirectoryEvents
Splunk
Change.All_Changes (Account_Management)WinEventLog:Security (4720, 4732)
CrowdStrike
UserAccountCreatedUserAccountAddedToGroup

A generic baseline worked out from the product type and weakness (CWE-287), not a detection. Check table and field names against your environment. Hunt queries for Sigma, Splunk, Sentinel and CrowdStrike are coming.

References