My Calendar <= 3.8.7 - Unauthenticated Privilege Escalation to 'mcs' Parameter via Reflected Shortcode Injection into 'above' Attribute

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-104798
StatePUBLISHED
AssignerWordfence
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-16 05:17:28 UTC
Updated2026-10-16 05:17:28 UTC
DescriptionThe 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.

Risk And Classification

Primary CVSS: v3.1 9.8 CRITICAL from [email protected]

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Problem Types: CWE-269 | CWE-269 CWE-269 Improper Privilege Management

VersionSourceTypeScoreSeverityVector
3.1[email protected]Primary9.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
3.1CNADECLARED9.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Joedolson My Calendar Accessible Event Manager affected 3.4.24 semver Not specified
CNA Joedolson My Calendar Accessible Event Manager affected 3.5 3.5.21 semver Not specified
CNA Joedolson My Calendar Accessible Event Manager affected 3.6 3.6.17 semver Not specified
CNA Joedolson My Calendar Accessible Event Manager affected 3.7 3.7.17 semver Not specified
CNA Joedolson My Calendar Accessible Event Manager affected 3.8 3.8.7 semver Not specified

References

ReferenceSourceLinkTags
plugins.trac.wordpress.org/browser/my-calendar/tags/3.8.6/my-calendar-navigation.php [email protected] plugins.trac.wordpress.org
plugins.trac.wordpress.org/browser/my-calendar/tags/3.8.6/my-calendar-search.php [email protected] plugins.trac.wordpress.org
plugins.trac.wordpress.org/browser/my-calendar/tags/3.8.6/my-calendar-shortcodes.php [email protected] plugins.trac.wordpress.org
plugins.trac.wordpress.org/changeset [email protected] plugins.trac.wordpress.org
plugins.trac.wordpress.org/browser/my-calendar/tags/3.8.6/my-calendar-search.php [email protected] plugins.trac.wordpress.org
www.wordfence.com/threat-intel/vulnerabilities/id/e8aa6ee7-525e-4458-9f5b-1e729... [email protected] www.wordfence.com
plugins.trac.wordpress.org/browser/my-calendar/tags/3.8.6/my-calendar-output.php [email protected] plugins.trac.wordpress.org
plugins.trac.wordpress.org/browser/my-calendar/tags/3.8.6/my-calendar-navigation.php [email protected] plugins.trac.wordpress.org
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: daroo (en)

Additional Advisory Data

SourceTimeEvent
CNA2026-10-02T13:27:02.000ZVendor Notified
CNA2026-10-15T16:25:37.000ZDisclosed

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