CVE-2026-76793 in Firebase Authentication Plugin
Summary
by MITRE • 08/22/2026
The Firebase Authentication WordPress plugin before 1.7.1 does not require the email address in an authentication token to be verified before matching it to a WordPress account and issuing a session, allowing unauthenticated attackers to log in as any user, including administrators.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 08/22/2026
The vulnerability identified in versions of the Firebase Authentication for WordPress plugin prior to release 1.7.1 represents a critical failure in authentication logic that fundamentally undermines the security model of the application. This flaw stems from an improper verification process where the system fails to validate the email address contained within the JSON Web Token issued by Google's Identity Platform against the actual user account being accessed. In standard secure implementations, when a token is presented for login, the service must ensure that the identity claims within the token match the target resource and that those claims have been verified by the trusted provider. However, in this specific implementation, the plugin accepts tokens containing any email address without confirming its authenticity or verifying it against Google's servers to ensure it belongs to a legitimate user account associated with the WordPress installation.
This technical deficiency allows for a straightforward authentication bypass attack vector where an attacker can forge or manipulate JWT payloads to include arbitrary email addresses corresponding to existing users on the target site, including those with administrative privileges. Since the plugin does not enforce strict binding between the token's subject and the verified identity from the provider, it trusts the client-supplied data implicitly. An unauthenticated actor can generate a validly signed token using known public keys or exploit misconfigurations in key management to create tokens that appear legitimate to the WordPress backend but contain fabricated email addresses pointing to high-privilege accounts such as administrators. This effectively neutralizes the multi-factor authentication benefits typically provided by Google Sign-In, reducing it to a simple possession-of-a-token mechanism which is trivially forgeable if keys are compromised or logic is flawed.
The operational impact of this vulnerability is severe, granting unauthorized access to sensitive areas of the WordPress dashboard and potentially full control over the website's content and configuration. By logging in as an administrator, attackers can modify site settings, inject malicious code into themes or plugins, steal user data, deface the website, or use the compromised server for further attacks such as phishing campaigns or malware distribution. The ease with which this exploit can be executed means that any WordPress instance running a vulnerable version of this plugin is at immediate risk of complete compromise without requiring complex exploitation techniques beyond basic token manipulation tools available in standard penetration testing frameworks.
From a classification perspective, this vulnerability aligns closely with CWE-287 Improper Authentication and CWE-345 Insufficient Verification of Data Authenticity as defined by the Common Weakness Enumeration standards. The failure to verify that the email claim in the JWT actually corresponds to a verified identity from the trusted provider constitutes a classic case of trusting unverified input during an authentication transaction. In terms of attack tactics, this behavior is consistent with MITRE ATT&CK technique T1078 Valid Accounts, where adversaries leverage legitimate credentials or tokens to gain initial access and maintain persistence within the environment without triggering typical intrusion detection systems that look for brute force patterns or invalid credential submissions.
To mitigate this risk, administrators must immediately upgrade the Firebase Authentication plugin to version 1.7.1 or later, which addresses these validation gaps by ensuring strict verification of email claims against Google's identity provider before issuing a session cookie. Additionally, organizations should implement defense-in-depth strategies such as enforcing multi-factor authentication at the WordPress level where possible and regularly auditing installed plugins for known vulnerabilities through automated scanning tools. It is also advisable to review server logs for any signs of anomalous login activity from unexpected IP addresses or user agents that may indicate exploitation attempts prior to patching, ensuring that no persistent backdoors were established during a potential window of exposure.