Admidio EUVD-2026-28266

Summary

The contacts_data.php endpoint uses a weaker permission check (isAdministratorUsers(), requiring only rol_edit_user=true) than the frontend UI (contacts.php) which correctly requires the stronger isAdministrator() (requiring rol_administrator=true) and the contacts_show_all system setting. A user manager who is not a full administrator can directly request contacts_data.php?mem_show_filter=3 to retrieve all user records across all organizations in the Admidio instance, bypassing multi-tenant organization isolation.

Details

The frontend page contacts.php and the backend data endpoint contacts_data.php have mismatched authorization checks for the "show all organizations" filter (mem_show_filter=3).

Frontend guard at modules/contacts/contacts.php:80:

if ($gCurrentUser->isAdministrator() && $gSettingsManager->getBool('contacts_show_all')) {
    // Only then is filter=3 ("All Organizations") shown in the dropdown
    $selectBoxValues = array(
        ...
        '3' => array('3', $gL10n->get('SYS_ALL_CONTACTS'), $gL10n->get('SYS_ALL_ORGANIZATIONS'))
    );
}

This correctly requires both isAdministrator() (rol_administrator=true) AND the contacts_show_all setting.

Backend check at modules/contacts/contacts_data.php:235:

} elseif (($getMembersShowFilter === 3) && $gCurrentUser->isAdministratorUsers()) {
    $mainSql = $contactsListConfig->getSql(
        array(
            'showAllMembersDatabase' => true,
            ...
        )
    );

This only requires isAdministratorUsers() which checks rol_edit_user=true - a weaker permission available to non-admin "user manager" roles. The contacts_show_all setting is never checked.

The critical difference between the two methods (from src/Users/Entity/User.php):

• isAdministrator() (line 1507): checks the rol_administrator flag - full system administrator
• isAdministratorUsers() (line 1625): checks rol_edit_user right - user management module access only

When showAllMembersDatabase=true reaches ListConfiguration::getSql() (at src/Roles/Entity/ListConfiguration.php:1022-1028), the generated SQL removes ALL organization filtering:

} elseif ($optionsAll['showAllMembersDatabase']) {
    $sql = 'SELECT DISTINCT ' . $sqlMemLeader . $sqlIdColumns . $sqlColumnNames . '
              FROM ' . TBL_USERS . '
                   ' . $sqlJoin . '
             WHERE usr_valid = true ' .
        $sqlWhere .
        $sqlOrderBys;
}

Compare with the default query which includes cat_org_id = $gCurrentOrgId to restrict results to the current organization.

The cross-org indicator subqueries at line 169 do correctly check isAdministrator(), so the member_other_orga columns return 0 - but this only affects display indicators, not the actual user data returned.

PoC

Prerequisites: An Admidio instance with at least two organizations sharing the same database. A user account in Organization A assigned to a role with rol_edit_user=1 but rol_administrator=0.

Step 1: Log in as the user manager account and capture the session cookie.

Step 2: Request all users across all organizations by directly calling the data endpoint:

curl -s -b 'PHPSESSID=<user_manager_session>' \
  'https://target/adm_program/modules/contacts/contacts_data.php?mem_show_filter=3&draw=1&start=0&length=100&search%5Bvalue%5D='

Expected behavior: The request should be rejected or return only current-organization users, since the user is not a full administrator and the frontend never offers filter=3 to non-administrators.

Actual behavior: The endpoint returns a JSON response containing all users from ALL organizations in the database, including:

• User UUIDs (usr_uuid)
• Login names (login_name)
• Email addresses (member_email)
• All configured profile fields (names, addresses, phone numbers, etc.)

Step 3: Verify that users from Organization B (where the attacker has no membership) appear in the results by checking the member_this_orga field - it will be 0 for cross-org users.

Impact

In multi-organization Admidio deployments (the primary use case for organization isolation), a user manager in one organization can exfiltrate the complete member directory of all other organizations sharing the same database. Exposed data includes:

• Full names and all configured profile fields
• Email addresses
• Login names (useful for credential attacks)
• User UUIDs (useful for targeting other API endpoints)

This completely bypasses the multi-tenant organization isolation boundary. The contacts_show_all admin setting (intended to control this feature) is also bypassed, meaning even instances where administrators have explicitly disabled cross-org viewing are affected.

Recommended Fix

Change line 235 in modules/contacts/contacts_data.php to match the frontend guard at contacts.php:80:

// Before (vulnerable):
} elseif (($getMembersShowFilter === 3) && $gCurrentUser->isAdministratorUsers()) {

// After (fixed):
} elseif (($getMembersShowFilter === 3) && $gCurrentUser->isAdministrator() && $gSettingsManager->getBool('contacts_show_all')) {

Additionally, as defense-in-depth, add an early rejection at the top of the file (after line 59) to block the filter value entirely for unauthorized users:

if ($getMembersShowFilter === 3 && (!$gCurrentUser->isAdministrator() || !$gSettingsManager->getBool('contacts_show_all'))) {
    $getMembersShowFilter = 0; // Fall back to default
}