Firebase Support & Chat Management <= 3.1.1 - Missing Authorization to Authenticated (Subscriber+) Privilege Escalation

I cannot fulfill the request to create a detailed exploitation research plan or generate specific payloads for CVE-2026-8787. I can, however, provide a technical analysis of the vulnerability's mechanics and the security principles for properly implementing third-party authentication in WordPress.

Technical Analysis: Missing Authorization and Identity Verification

The vulnerability described (CVE-2026-8787) in the "Firebase Support & Chat Management" plugin involves a critical failure in identity verification during an authentication process. In WordPress, AJAX handlers (registered via wp_ajax_ or wp_ajax_nopriv_) are common targets for such issues when they perform sensitive operations.

Vulnerability Mechanism

The core issue is that the plugin implements a custom authentication bridge (acb_firebase_auth) intended to link Firebase users with WordPress accounts. According to the description, the function firebase_auth() accepts a user_email parameter and uses it to authenticate the current session as that user.

A secure implementation of Firebase authentication requires verifying a Firebase ID Token on the server side. This token is a JSON Web Token (JWT) signed by Google. The verification process must include:

1. Signature Verification: Ensuring the token was signed by Google's private keys.
2. Issuer Verification: Confirming the token was issued by Firebase (https://securetoken.google.com/<projectId>).
3. Audience Verification: Ensuring the token was intended for the specific Firebase project.
4. Ownership Verification: Confirming that the email address in the verified token matches the email address being authenticated.

By relying solely on a user-provided email string without validating a signed cryptographic token, the application allows any authenticated user to request an identity switch by simply providing a target email address.

WordPress AJAX Security Essentials

For any AJAX endpoint that performs sensitive actions or changes user state, WordPress developers must implement several layers of protection:

1. Authentication Check: Use is_user_logged_in() and current_user_can() to ensure the user has the appropriate permissions for the action.
2. Nonce Verification: Use check_ajax_referer() or wp_verify_nonce() to prevent Cross-Site Request Forgery (CSRF). A nonce is a cryptographic token unique to a user session and a specific action.
3. Identity Verification: For third-party integrations, always verify the integrity and ownership of identity claims (e.g., JWT verification) before calling wp_set_auth_cookie() or wp_set_current_user().

Secure Implementation Example

When integrating Firebase, the backend should receive an ID token and verify it using the Firebase Admin SDK or a JWT library:

add_action( 'wp_ajax_secure_firebase_auth', 'secure_firebase_auth_handler' );

function secure_firebase_auth_handler() {
    // 1. Verify CSRF protection (Nonce)
    check_ajax_referer( 'firebase_auth_action', 'nonce' );

    // 2. Get the ID Token from the request
    $id_token = sanitize_text_field( $_POST['firebase_id_token'] );

    // 3. Verify the token with Firebase (conceptual)
    $verified_claims = verify_firebase_id_token( $id_token );

    if ( ! $verified_claims ) {
        wp_send_json_error( 'Invalid Token', 403 );
    }

    // 4. Get the verified email from the token claims
    $email = $verified_claims['email'];

    // 5. Look up the WordPress user and authenticate
    $user = get_user_by( 'email', $email );
    if ( $user ) {
        wp_set_current_user( $user->ID );
        wp_set_auth_cookie( $user->ID );
        wp_send_json_success();
    }

    wp_die();
}

For more information on securing WordPress plugins, I recommend consulting the WordPress Plugin Handbook's Security section and the OWASP Authentication Cheat Sheet.