Description
The My Calendar – Accessible Event Manager plugin for WordPress is vulnerable to Privilege Escalation in all versions up to, and including, 3.8.7. The public `mcs` GET parameter is reflected into post content unsanitized before WordPress core's `do_shortcode` filter runs, allowing an unauthenticated attacker to inject a nested `[my_calendar above=...]` shortcode; `mc_generate_calendar_nav()` then splits the `above` attribute on commas and dispatches each element via `call_user_func()` with no authentication, authorization, or callable allowlist check. This makes it possible for unauthenticated attackers to invoke arbitrary loaded PHP functions, enabling a call chain in which the shortcode `$params` array is passed to `edit_user()` — which PHP coerces to integer `1` as the `$user_id` argument — overwriting the credentials of the initial Administrator account (user ID 1) and granting the attacker full wp-admin access. Exploitation is trivially reachable via the plugin's auto-generated `/my-calendar/` page, which is publicly accessible by default upon plugin activation.
References
- www.cve.org/CVERecord ↗
- nvd.nist.gov/vuln/detail/CVE-2026-104798 ↗
- plugins.trac.wordpress.org/browser/my-calendar/tags/3.8.6/my-calendar-navigation.php ↗
- plugins.trac.wordpress.org/browser/my-calendar/tags/3.8.6/my-calendar-navigation.php ↗
- plugins.trac.wordpress.org/browser/my-calendar/tags/3.8.6/my-calendar-output.php ↗
- plugins.trac.wordpress.org/browser/my-calendar/tags/3.8.6/my-calendar-search.php ↗
- plugins.trac.wordpress.org/browser/my-calendar/tags/3.8.6/my-calendar-search.php ↗
- plugins.trac.wordpress.org/browser/my-calendar/tags/3.8.6/my-calendar-shortcodes.php ↗
- plugins.trac.wordpress.org/changeset ↗
- www.wordfence.com/threat-intel/vulnerabilities/id/e8aa6ee7-525e-4458-9f5b-1e729afe448c ↗
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This product uses the NVD API but is not endorsed or certified by the NVD. CVSS scores do not establish exploitation.